Jump to content

Hesitation woes


Ultrafinder
 Share

Recommended Posts

This is also posted on AC, for the people that only post here I have almost gone section 8 with this problem. I need some help. First I have a 1994 SE with 230,000 mi.. Last year my truck would miss (stutter) a little while idling w/ air cond and only happens after warm-up. Not too bad happened maybe 1 or 2 times a week. That lasted a few months then it started to happen more frequently to all the time with a/c on. I band-aided it by turning the a/c off at lights. The problem progressed to stuttering whether a/c was on or not at idle. Now the stuttering is so bad it almost stalls and when I am just cruising down the road it stutters. I replaced the timing belt just in case and it didnt help. So over a year it progressively got worse to the point I can't drive it any more. I had a preemie baby 5 mos. ago and he is finally coming home next week and I need my truck bad...This what I have done so far. I changed the O2 about a year ago which I have recently unplugged to see if the stutter goes away and it didn't. I changed the plugs, rotor, cap and air filter about 6 mos ago. For good measure I changed the cap and rotor again yesterday, no help. Also changed fuel filter. I have a FSM and changed the temp. sensor this morning which didn't help. I cleaned and tested the MAF, it's good. I checked and rechecked for air leaks and couldn’t find any. Finally, I waited for last and changed the IACV which wasn't cheap, that didn't help either. I also did the Sea Foam thing.

I can't figure out why this happens only after warm-up and there is this loud popping noise coming from behind the motor every time the idle stutters almost like an elect. arcing sound. It's not the 6 plug wire or the fuel regulator. I have a stethoscope for just these times and as close as I could get to the sound it seemed to be coming from right around the back injector. I can't tell if the drop in idle is causing the sound or the sound is causing the drop in idle. As you see, I have run out of things to check and it's getting expensive changing parts. I don't know if this helps but the gauges are starting to act a little funny too. If you have some ideas I could sure use them.

Link to comment
Share on other sites

Yes, he said that. (MAF)

 

Ultrafinder....I'd try to find a known good #6 plug wire, and throw that on there. If it's an arcing sound it could be that the wire is arcing on the block.

Link to comment
Share on other sites

see if your exhaust gas recirculation valve is sticking too. do you have a factory service manual? they have really good troubleshooting sections.

Link to comment
Share on other sites

I have the FSM that I downloadedit has been a great help. I just got home and going to check the EGR now also going to unplug the O2 sensor before it warms up and see if that makes a difference. If the CAT is blocked up will it get worse as it heats up? I should of stated in my original post but, there are no codes or codes stored.

 

 

not a word about ECU codes. hmmm
Link to comment
Share on other sites

No codes at all? Uhm... that's strange. Blocked cat might be a thing to check... what about the fuel pump or injectors? They could be going south on you?

Link to comment
Share on other sites

I haven't checked the fuel pump or injectors because I didn't think they would act up only after warm up. wouldn't they act funny all the time? I saw something on the news about gas stations using 10% Ethanol in their gas and some cars were reported having serious problems as result.

 

 

 

 

No codes at all? Uhm... that's strange. Blocked cat might be a thing to check... what about the fuel pump or injectors? They could be going south on you?
Link to comment
Share on other sites

10% ethanol is normal in all US cities that have cold weather. no adverse effects.

 

bad injector should throw out a code. should but may not. same with O2 and all the rest.

 

missing could be out of time, sparking wires.. leaky va. plugged fuel filter. worn plugs, bad cap, bad rotor... lot's of things. have to start checking off these things and eventually you will stumble into it. :)

Link to comment
Share on other sites

nope on the injector Q. they may act up cold or hot, all the time or here and there. never know.

 

cat. there really sin't a way to test it. plugged cat will make it run like crap either hot or cold but you should have no power basically. if you can redline this thing and make it accelerate good then it's not the cat.

Link to comment
Share on other sites

Actually, 10% ethanol makes my girl run like @!*%... well, not really, but I get a LOT less kick out of the old gal...

 

There are a handful of stations around me (PA) that sell 5% or non-ethanolated fuel... when I use those, I get better mileage, more power, better accelration, better throttle response... generally, I think Ethanol is fskcing up my truck :(

Link to comment
Share on other sites

As posted on AC.

Happy to say I finally fixed it. It was a stuck injector. They sure can give off some weird symptoms. I fixed it with Sea Foam. I emptied my fuel filter and filled it with S.F. Ran it hard for about 20-30 min. and it idled perfect as a matter of fact since I've had it I don't think it ever ran this good. I'm going to do it again tomorrow just for good measure. Anyone with any symptoms like I had spend the $8 and do this first. Thank You all that replied. I hope this helps others.

Link to comment
Share on other sites

Ultrafinder -

 

You just... poured the seafoam directly into the fuel filter? Didn't that make it run real hard... I mean, SeaFoam won't run an engine on it's own will it?

 

Tell me a little more about what you did - I'd love to run SeaFoam thru my truck, just not really sure how to do it (I'm using a LucasOil fuel treatment, but I think SeaFoam might work a bit better in such a concentrated fashion)

Link to comment
Share on other sites

Yeah, That's exactly what I did... I removed the filter and filled the whole thing up w/ SF. It might of ran with a very small bit of hesitation but, nothing big. The fuel filter is under pressure so enough fuel will mix in to run. The beauty of this is that anyone that wants to clean the injectors can do it. I wish I did this first :suicide:

 

 

 

Ultrafinder -

 

You just... poured the seafoam directly into the fuel filter? Didn't that make it run real hard... I mean, SeaFoam won't run an engine on it's own will it?

 

Tell me a little more about what you did - I'd love to run SeaFoam thru my truck, just not really sure how to do it (I'm using a LucasOil fuel treatment, but I think SeaFoam might work a bit better in such a concentrated fashion)

Link to comment
Share on other sites

Yeah, That's exactly what I did... I removed the filter and filled the whole thing up w/ SF. It might of ran with a very small bit of hesitation but, nothing big. The fuel filter is under pressure so enough fuel will mix in to run. The beauty of this is that anyone that wants to clean the injectors can do it. I wish I did this first :suicide:

 

If i can find who sells the stuff here im going to try this too. my rig was running like crap till i figured out that the screws holding the injectors in wasnt tight. previous owner did a bang up job stripping those out for me. but putting that stuff in the filter sounds like a great way to get the best cleaning.

Link to comment
Share on other sites

  • 2 weeks later...

mine is still runnin like crap. idles great now that the injectors are tight and all the vacuum lines are proper. timing is dead on, all electrical connections clean and tight except im misssing the clip that locks in the plug for the MAF. but it doesnt appear to be backing out, cleaned that also with a q-tip. ran sea foam through it. my problem is acceleration, only way to get going is pumping the gas , or it lurches and jerks and jumps. im sure i look like im driving 5 speed for first time taking off from lights. no codes on my ecu either. i dont know what else to check. egr is functioning fine, no vacuum leaks. new plugs, new wires. just no stompie on the gas or it chokes.

 

 

 

 

 

 

 

miles and miles of AZ desert to explore

Link to comment
Share on other sites

Red87path, what about:

 

Compression under load

ECU timing changes (heavy acceleration changing the ECU timing?)

Have you checked for prefire/detonation/misfire?

 

I'm really not sure what else it could be...

Link to comment
Share on other sites

As the Sea Foam seemed to band aid the hesitation for a while I ultimately ended up changing a stuck injector. Of course it was #6 but, it's done and runs great although, I made a stupid mistake as posted in another topic. I got a great price for a brand new injector from Advance Auto $38. I couldn't believe it so I asked to him to verify it was new the guy said yes. I think I got a great deal. If any one needs injectors price them there first. I went through hell trouble shooting this thing. Anyone with symptoms like mine think about a stuck injector . There were no codes and the resistance checked out fine @13.5 ohm. Hope everyone else has a better time diagnosing than I did.

 

 

 

Red87path, what about:

 

Compression under load

ECU timing changes (heavy acceleration changing the ECU timing?)

Have you checked for prefire/detonation/misfire?

 

I'm really not sure what else it could be...

Link to comment
Share on other sites

  • 2 months later...
Red87path, what about:

 

Compression under load

ECU timing changes (heavy acceleration changing the ECU timing?)

Have you checked for prefire/detonation/misfire?

 

I'm really not sure what else it could be...

how would i check any of these things? been a while i know since you posted this but i can never find the posts i have put up.

Link to comment
Share on other sites

mine is still runnin like crap. idles great now that the injectors are tight and all the vacuum lines are proper. timing is dead on, all electrical connections clean and tight except im misssing the clip that locks in the plug for the MAF. but it doesnt appear to be backing out, cleaned that also with a q-tip. ran sea foam through it. my problem is acceleration, only way to get going is pumping the gas , or it lurches and jerks and jumps. im sure i look like im driving 5 speed for first time taking off from lights. no codes on my ecu either. i dont know what else to check. egr is functioning fine, no vacuum leaks. new plugs, new wires. just no stompie on the gas or it chokes.

miles and miles of AZ desert to explore

Have you checked the TPS (Throtle Position Sensor) and/or the fuel presure regulator? I had an oldsmovile once that was doing the same thing and it was a dead spot in the TPSjust off the idle position. If the fuel presure regulator is stuck open the fuel presure will drop when you accelerate and stall the engine.

Link to comment
Share on other sites

Have you checked the TPS (Throtle Position Sensor) and/or the fuel presure regulator? I had an oldsmovile once that was doing the same thing and it was a dead spot in the TPSjust off the idle position. If the fuel presure regulator is stuck open the fuel presure will drop when you accelerate and stall the engine.

its got a new tps but i think it needs adjusted , as for the fuel pressure reg, how do you tell if it is stuck open? havent thought about either of these things.

Link to comment
Share on other sites

its got a new tps but i think it needs adjusted , as for the fuel pressure reg, how do you tell if it is stuck open? havent thought about either of these things.

There are 3 ways to check the FPR that I know of; the first one is to disconect the vacum line of the FPR and look at the line, if it is wet iside the FPR is bad. The secon is to hook a presure gauge to the fuel rail,start the vehicle and whatch the presure when you rev up the engine(acording to my manual, the presure should read 34 PSI at idle and 43 PSI the moment the throttle plate is fully open(same as having the key on with the engine off). The third way is to pull the FPR out and use a vacum pump to aply vacum to the diafram and see if the plunger moves. The FPR is a "normally closed" valve so it should be closed at rest and open when vacum is aplied.

 

PS. My factory service manual has this other test to diagnose the problem:

 

 

With the engine running, disconect the injector plugs one at a time; the engine should have a momentary drop in speed with each one. If any of the cylinders doesn't ; pull the distributor out (don't forget to TDC piston #1 First :-) keeping the small plug connected(unplug the coil to prevent detonations), then turn the ignition switch on and slowly rotate the gear on the distributor (Doesn't matter wich way ) each injector should make a sound. If any of them doesn't then the problem is with the injector or with the crank angle sensor (inside the distributor)

If all above checks out good then the book recomend checking the ECU harness conector and the pin terminals for damage or poor conection then check the ecu power and ground and if all checks ok then try a known good ECU.

 

To adjust the TPS on a KA24E Loosen the mounting bolts,start the engine and let it warm up to operating temperature; then use a voltmeter to check the output voltage. set the ouput voltage to .4 - .6 volts by rotating the body of the TPS when you get it right shut off the engine and tigten the mounting bolts then disconect the TPS for a few seconds and reconect it and you are done.

 

I hope this helps :happy:

Edited by Legalalien
Link to comment
Share on other sites

There are 3 ways to check the FPR that I know of; the first one is to disconect the vacum line of the FPR and look at the line, if it is wet iside the FPR is bad. The secon is to hook a presure gauge to the fuel rail,start the vehicle and whatch the presure when you rev up the engine(acording to my manual, the presure should read 34 PSI at idle and 43 PSI the moment the throttle plate is fully open(same as having the key on with the engine off). The third way is to pull the FPR out and use a vacum pump to aply vacum to the diafram and see if the plunger moves. The FPR is a "normally closed" valve so it should be closed at rest and open when vacum is aplied.

 

PS. My factory service manual has this other test to diagnose the problem:

With the engine running, disconect the injector plugs one at a time; the engine should have a momentary drop in speed with each one. If any of the cylinders doesn't ; pull the distributor out (don't forget to TDC piston #1 First :-) keeping the small plug connected(unplug the coil to prevent detonations), then turn the ignition switch on and slowly rotate the gear on the distributor (Doesn't matter wich way ) each injector should make a sound. If any of them doesn't then the problem is with the injector or with the crank angle sensor (inside the distributor)

If all above checks out good then the book recomend checking the ECU harness conector and the pin terminals for damage or poor conection then check the ecu power and ground and if all checks ok then try a known good ECU.

 

To adjust the TPS on a KA24E Loosen the mounting bolts,start the engine and let it warm up to operating temperature; then use a voltmeter to check the output voltage. set the ouput voltage to .4 - .6 volts by rotating the body of the TPS when you get it right shut off the engine and tigten the mounting bolts then disconect the TPS for a few seconds and reconect it and you are done.

 

I hope this helps :happy:

 

it should , its all new info i havent come across elsewhere. thanks

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

×
×
  • Create New...