1995 Trouble Climbing Hills / Significant Slowdowns

[Revco]

Hey guys,

 

I've got a '95 Pathy SE that's expeirencing an issue I'd like your opinion on. Been experiencing issues at the top end going up hills where I seem to lose a tremendous amount of power. The vehicle will consistently lose speed up a good size hill, going from 75MPH (yay, Montana!) to as low as 55MPH, depending on the size of the hill. Problem doens't seem to be present in lower gears and slower speeds, only in 4th/OD that I can tell, as I haven't had any issues trail running. Problem happens with power switch enabled or disabled, explicit OD on or off. What's odd is that the kickdown/downshift doesn't seem to function properly most of the time when this is happening, but when I can get it to kickdown to a lower gear, the rig still doesn't have the "ooph" to get it up to speed. Also, I think maybe the issue is still present, but far more subtle, at high speed over flat terrain where CC (or manual holding of speed) stuggles to maintain a consistent speed over the terrain.

 

Relevant info...I've been getting O2 sensor SES's for about 8K miles that I've been ignoring due to a relatively infrequent/intermittent nature of them. Those SES's have largely quit in the last few weeks, but it seems to me the timing of this issue has exceeded the start and end of the O2 sensor SES codes. I wouldn't think this could cause an issue this severe, but I've seen a couple people report issues somewhat similar with the O2 sensor. Also, I had my tranny rebuilt approximately 10K miles ago, seems to be in good shape, but wanted to mention it in case it's relevant...but no tranny codes are thrown. I saw another mention of a camshaft sensor in a similar symptom. Seems to me the last time I replaced the O2 sensor was maybe 80-100K miles ago and is my third, including stock. She's also got 260K miles on her, so I fully expect that it could be something fairly uncommon.

 

Recent troubleshooting includes a full tuneup. New wires, plugs, disty cap/rotor, PCV, fulids, etc. Engine is relatively leak free after full front/rear/valve cover gasket replacement. Engine has good power in lower gears, still has the "ooph" at lower speeds . Wheel travel is excellent and likely not related. Oil and coolant look good, no reason to suspect head gasket or anything like that.

 

My mechanic hasn't really addressed the issue over two visits as whatever it is isn't throwing a code, other than that infrequent O2 sensor. I'm thinking O2 sensor, but I don't want to randomly throw $250 at the issue if I don't have to, but I also want to fix the problem. Am I on the right track...can a faulty O2 sensor truly throw these symptoms? Anything else to consider? Thanks guys!

[ebayfish]

Have you tried clearing all the SES codes, the computer may just be doing something odd. I had issues with sputtering and found 2 issues that helped alot, first the EGR was sticking, so I cleaned that, also replaced the vacuum lines to it in case there was any rot. Second, the previous owner put spark plugs in, but never gapped them, they were all at 0.070-75. I went ahead and replaced them & regapped I think to 0.032 & it runs like a *new* 19 year old car!

[Alkorahil]

If you did not replace the fuel filter when you did the tune up I would replace that along with the engine coolant temp sensor.

 

I would also check the vehicle timing with a timing light.

 

Check to see if the vacuum hose near the firewall that goes from the back of the intake plenum to the fuel pressure regulator is there/not loose/or has cracked and frayed ends.

 

Double check after the vehicle is hot and been run around for a bit if the transmission fluid is at the proper level.

 

 

But most importantly, a bad or marginally working O2 sensor will definately suck power from the truck as the ECU cannot make the proper adjustments to air/fuel mix.

 

 

[Terranovation]

Also try depressing the accelerator pedal and see if you hear a click sound. That's the sound that tells you the trans should kick down a gear. You can test this without the engine running.

[Revco]

Thanks for the thoughts.

 

I did check the kickdown switch, I hear the click but haven't actually tested the switch for operation. I'm less inclined to think it's a switch issue, since things do downshift properly at lower speeds and sometimes downshifting does work, particularly in lower gears and lower speeds.

 

I checked the old plugs and they were gapped pretty close, around .041 if I remember right when I pulled them. Gapped new ones to .039 to be on the low end and to allow for a bit of expansion. I don't get any rough idle or what appears to be ignition issues, that I can tell. Timing was pretty darn close to 15 BTDC last check, but I suppose it could have slipped in the last year or so. I've got about 50K on my current T-Belt, so doubtful that it slipped...but worth at least checking to be sure. I do occasionally get a bit of knock at lower speeds, so I've been thinking about checking timing anyway and adjusting if necessary. Also, fuel filter was done ~10K miles ago and regularly changed...it's on my list of typical maintenance items to replace this go-round, at least to eliminate something stupid.

 

As for clearing SES's, I haven't been clearing them, so I'll look into that...but my computer hasn't traditionally thrown me trouble. Good call on cleaning up the EGR valve, I'll learn how to do that and put it on the agenda. I wouldn't call myself a good enough self-mechanic to diagnose vacuum lines, but that's one of the things I have on my list for my mechanic to consider after I get done eliminating what I can. I can at least see if they're deteriorating and obviously experiencing an issue...but, nothing I've noticed crawling around recently hot and cold, but also haven't followed them back past what's typically visible from the engine bay just yet. I'll do that.

Thanks for the ideas...gives me a few things to knock off between now and next week when I've scheduled another visit with the mechanic. The unfortunate thing is I have to drive almost 90 miles round trip into Idaho to find a suitable mountain to reproduce the problem consistently! Eh, another road trip....

Edited July 10, 2014 by Revco

[Nefarious]

You can get an ngk o2 sensor on ebay for about 60$. 250 is way over priced! If you have been having an indication of o2 sensor then I would start there...I've had bad o2 sensors that never threw any codes personally. Keep in mind they really are old technology ecus, sometimes we as owners have to be smarter than the computer running things

[Precise1]

Agreed, but they might be called NTK when you search for them. NGK=plugs, NTK=O2 sensors...

 

B

[adamzan]

You can buy them on rock auto even cheaper. Ntk o2 sensor for like 40 dollars. Either get ntk or bosch. Bosch is oem though.

[Revco]

Ah, sorry, that was a typo at $250. Meant $150 as I was looking at the price from the dealership. $40 sounds much better, confirmed on RockAuto at $35 and change.

 

How difficult is it to change out the sensor with Thorleys installed? I remember the last couple times my mechanic complaining it was a bit tough to get done right. (I almost think the headers need to be retapped maybe, like they got galded or something way back when.) I don't see a procedure in the FSM, but it looks fairly straight forward, minus the metal connection, which I'm not 100% sure how it's fastened on there. Is it compression? What? Anything to be aware of or is it just a pull and replace kind of job? (That's mostly the work I do, quick and fast...still not bold enough to take on big projects or one's that require special tools and such as the rig's my daily driver.)

 

Appreciate the insight!

[ThaBigPerm]

Aside from the tune-up tips, how much weight were you carrying? I ask because I just experienced this first-hand on my trip to Colorado. I halfway expected it, being underpowered from the factory as it was/is. I guestimate I was hauling around a thousand pounds of camping gear, fuel, me and dog, if not a tad more. On those highway mountain passes, climbing rapidly up to around 12,000ft, she was lugging hard. 75mph hill climb starts. Engine begins to lug, speed drops. TC slips out of lockup, speed still bleeds as hill gets steeper. Trans downshifts out of OD to 3rd. Decide to lock OD out, so TC can lock in 3rd. It does, but speed keeps falling. Below 55mph, TC comes back out of lockup. Speed keeps bleeding, manually shift down to 2nd and can maintain around 40mph at @ 3000ish RPM, and that's my top speed. Engine gets warm (doesn't overheat, just needle moves up noticeably, even with AC off). Altitude + "warmer than normal" engine = even less power than it had originally, which wasn't much. I didn't chalk this up to a tuning problem so much as just ... "the way it is" with this vehicle's engine. Runs fine on the level/unloaded, and off road in 4low happily cralwed over every obsticle in front of it, even up to 12,800ft. It was just maintaining highway speeds on mountain passes, loaded and at altitude, that taxed it. I let leverage (gear ratio) be my friend - I let it run at its peak torque (around 3k RPM) in a lower gear and lower speed rather than beat on it in a higher gear trying to get it to maintain speed at 1800rpm.

Edited July 10, 2014 by ThaBigPerm

[adamzan]

The o2 sensor is in the intermediate pipe so I don't know why you would have to touch the headers. Unless your mechanic put the o2 sensor in one of the headers, that would cause a alot of issues.

[Revco]

I haven't been hauling anything when this happens, practically an empty truck with a single passenger. Not big people, by any means either, so we're not talking less than 350lbs total passenger weight. I would call the symptom abnormal...driven this rig over 200K miles through all sorts of mountainous terriain including the Rockies probably a hundred times, so I know her pretty well. I usually have enough power to maintain a good speed up a hill, maybe a little loss but not a what feels like a rapid decline like this does, struggling and completely unable to keep a speed. The problem's happened hot or cold, we get some pretty good winters here and I can recall this issue from some sub-zero trips...so I don't think temps play much.

 

Just checked the timing and it looks like it's off by almost 8-10 degrees BTDC...not sure how that happened (or even how it's running seemingly well otherwise?), but prolly my mechanics jacked it up when they did my valve cover gaskets here awhile back. I checked it sometime after my last timing belt change, so something's obvisously been changed since since that's a pretty good drift. Gonna have to correct that, first, as that could have a lot to do with things. Picked up a new Bosch O2 sensor tonight, gonna give it a go I think since it's obviously probably on it's way out. Couldn't find an EGR gasket and a bit concerned to take it off for a good cleaning without a suitable replacement on hand, so that's gonna have to wait I think. Checked most of the vacuum hoses that I could ID and things look decently OK, no major visual problems anyway...might have to break a hose out and go fishing for leaks to be sure.

 

Anyway, thanks for the idea on checking the timing, it's something I bypassed thinking there wasn't any cause to change it and therefore little reason to think it might be off.

[Kingman]

Consider this about the oxygen sensor. The ECU is looking for readings from it that were within a certain parameter and the readings are meant to vary. If the sensor's output no longer varies but is within the parameters, the ECU won't see that as an issue but the information being given is still bad. The light coming on could be from the sensor quitting for a second here and there.

 

A can of brake cleaner will expose vacuum leaks. When it's sucked into the engine it will make it race for a few seconds.

[ThaBigPerm]

I haven't been hauling anything when this happens, practically an empty truck with a single passenger. Not big people, by any means either, so we're not talking less than 350lbs total passenger weight. I would call the symptom abnormal...driven this rig over 200K miles through all sorts of mountainous terriain including the Rockies probably a hundred times, so I know her pretty well. I usually have enough power to maintain a good speed up a hill, maybe a little loss but not a what feels like a rapid decline like this does, struggling and completely unable to keep a speed. The problem's happened hot or cold, we get some pretty good winters here and I can recall this issue from some sub-zero trips...so I don't think temps play much.

 

Just checked the timing and it looks like it's off by almost 8-10 degrees BTDC...not sure how that happened (or even how it's running seemingly well otherwise?), but prolly my mechanics jacked it up when they did my valve cover gaskets here awhile back. I checked it sometime after my last timing belt change, so something's obvisously been changed since since that's a pretty good drift. Gonna have to correct that, first, as that could have a lot to do with things. Picked up a new Bosch O2 sensor tonight, gonna give it a go I think since it's obviously probably on it's way out. Couldn't find an EGR gasket and a bit concerned to take it off for a good cleaning without a suitable replacement on hand, so that's gonna have to wait I think. Checked most of the vacuum hoses that I could ID and things look decently OK, no major visual problems anyway...might have to break a hose out and go fishing for leaks to be sure.

 

Anyway, thanks for the idea on checking the timing, it's something I bypassed thinking there wasn't any cause to change it and therefore little reason to think it might be off.

 

As for vacuum hoses, there are quite a few (plus coolant) under the plenum that can only be accessed by removing it. PITA for sure, but mine only had 138k miles when I pulled mine and most of the hoses were cracked/cracking and some crumbled in my hands when I tried to remove them. Replaced them all with bulk hose cut to length. On a side note, an EGR gasket came with my plenum gasket if I'm not mistaken. While I had it off, went ahead and did valve cover gaskets (might as well).

 

 

[ebayfish]

I picked up an EGR from O'Rielly for about $2.79. There are several detailed videos on youtube on how to clean an EGR, takes maybe 30 minutes. BTW, while on a subject of speed, how fast could a stock Pathy go? I've pushed this one to 90 and still seems to have some pedel.

[94 Pathy]

I had issues like that with both my Pathy's. Replaced O2 sensor and ran like a charm. YES, ROCKAUTO is a pocket saver. I get ALL my parts through them if I can & wait time isn't long at all. I've had it say 5-7 days & had it with-in 2-3 days. Good luck!

[94 Pathy]

Yeah, I've had mine running 90 while letting my road rage get the best of me & pulled a jack-ass over on the side of the road at that speed. Yep, I was a road rage ass years ago. Not worth it anymore.

[Revco]

Phew. Got that O2 sensor in. I originally mistook the sensor for the exhaust recirculation connected to the headers, mainly because I couldn't see it since the cross member was in the way. What a *%&$...that thing was really in there! Coincidentally, I noticed in my Haynes service manual that the O2 sensor is a regular maintenance item at 60K mile intervals, didn't know that! So, the probable 100K+ miles probably was a bit beyond it's capability and it needed replacement anyway. She did pick up quite a bit it would seem from just that change (haven't adjusted timing yet), but I'll have to make a trip a bit out of town to really test it. Closest good mountain to me where I could reproduce it is a 45 miles west into Idaho. Looks like it's time for a road trip!

 

I tested the EGR valve and it appears to be doing what it should. When I press the diaphram, the engine stutters...returning to "normal" when it's released. I tested it after warmup, too, and similar behavior. I'll get it off and give it a good cleaning, maybe next weekend, after I can get a gasket in. Sometimes finding specialized parts can be a challenge here...checked five stores and nada on the gasket.

 

I've hit a good 90 in mine, not an incredibly uncomon thing here in Montana when you're trying to pass someone going 75.

[Revco]

I wanted to provide an update on this. I'm not convinced the O2 sensor fixed the problem, although I had kind of a poor 70MPH test drive, given a fairly windy test track up in the Rockies. But, in a new development, I was able to get something different on the computer this time...only after I replaced the presumably faulty O2 sensor. Got a coolant temp sensor code (1 long 3 short, I think...not looking at the manual ATM) after the test drive...so I have one of those coming in a bit later this week and will get it swapped out. So, maybe my computer was malfunctioning...I did reset the codes before the test drive, just in case.

 

Further troubleshooting steps taken, just in the interest of putting this behind me. I Seafoamed the intake and crankcase, also cleaned up the fuel injectors again...just to kind of get the engine in top shape. TBI looks fairly clean, and just in case I cleaned my MAF again. Got the fuel filter done, seen worse but it was close enough to time. Oh, and I timed the vehicle here awhile back prior to the road test, spot on 15BTDC and seems to be holding. Did about as good of a vacuum check as I think I can perform..still putting off ripping that EGR valve off there, but will do if the post-code resolution test doesn't go well.

 

Overall, I can tell she's running better doing pretty much a complete 100K maintenance cycle (minus t-belt) at 60K, but that's probably to be expected. I'm really hoping replacing this coolant temp sensor might do something for me. From what I've read about their failures, I haven't seen identical symptoms reported when people have issues with these...but who knows!

 

Appreciate all the advice, think I got most things knocked out from the suggestions so far. I'll report back when I know more! Hope to find some time to take another road trip here next weekend.

[sunovertone]

Hello reading your post, have the same issue with my pathy. Did you get things resolved, what was the issue?

[Nefarious]

Have you done a compression test? That should always be the first line of diagnosis when power loss is an issue. Doing a dry and the wet test can really diagnose many problems, always best to start with the free and easy stuff. It also eliminates anything mechanical as the issue.

 

There is a procedure in the factory service manual to test the coolant temp sensor. There is also a test mode in the ecu for testing the o2 sensor but I just read that you replaced that already.

 

The only way the egr is going g to cause you to lose power is if it's stuck in the open position letting exhaust gas constantly re circulate under engine load.

Edited August 23, 2014 by Nefarious