94 sierra 5.7 excess fuel at idle, lopes

[strmn94]

well here is the problem, my 94 gmc, has a loppy idle. like it has a race cam.
here is what has been done to it. timing chan replaced.
had a back fire adn had to replace fuel pump.
cleaned injector filter screens, rebuilt regulator, replaced fuel filter, plugs, wires, and still has a loppie idle. it is getting too much fuel at idle. bring rpm up and it smooths out.
have been getting a code 54, low fuel pump relay voltage.
i have also replaced the fuel pump relay also.
the truck has 190,000 miles on it. the compression is 150 psi per cylinder.
i have headers on it and no cat. convertor. has a good free flow exhaust, and has lots of power still, but the rough idle has got me puzzled. i even cleaned up the idle air solinoid. the only thing i have not done yet is check the ecm connections, or the throttle position switch.
the engine has never had any major work done to it except for the timing chain.
the ignition module is the original one also.
any suggestions would be appriciated.
the other option is i would do a rebuild of the engine, but it has been working great, til when it backfired, and since then there has been the fuel problems.
the injectors are the originals also.

[horse482]

Have you checked the side to side play in the distributor shaft?

[2000CAYukon]

Just curious, why do you think it is getting too much fuel? Do you smell fuel? Is it black around the tail pipes?

It is a lope or a misfire? Does the problem happen with engine hot or cold? Or both?

//2000CAYukon

[strmn94]

well to the first reply, the distribitor shaft is fine. as i said i have replaced the timing chain and sprokets. the shaft has no play.
to the second responce.
the way i know there is alot of fuel, is you can see the excessive fuel spray from the injectors now. never seen it before. i bought this truck new in 94.
the lope is not from a missfire. plugs, wires, cap and rotor was just replaced over the weekend. also rebuilt the regulator on the TBI unit.
the lope sounds like there is a large lift long duration cam in it, and there is not. i have been around the automotive for a long time. took auto shop in high school, worked in 2 differant garages, also worked on the funny car in my avitar for 4 years. i have rebuilt a few engines. and i have also hopped up a couple of them myself.
the lope goes away when you are running, say about 1000 rpm. it is loping at idle. bring the rpm up and it smooths out. the inside of the exhaust has a slight black build up. looking at the plugs, i can tell that it is showing a little rich on about 3 to 5 cylinders. the one thing i have not done is replace the injectors, they are not cheap.
one thing i have not tried is to clean the ECM connections yet, since I and everyone else that has driven the truck smokes.

any other ideas are welcome.

i also replaced the EGR valve and solinoid a couple of years ago.
the engine has never been overhauled. fuel filter was replaced when the fuel pump went out, and caused a back fire.

[fuzzypuppy]

Hello, I had the same problem with my 91 truck 2 separate times, once was the o2 sensor, second was the temp sensor, not the one for the gauge but the one on the intake. either one going bad will set your comp to closed loop mode which dumps the fuel into the engine causing the rich mixture, a problem with your egr will do the same, are you sure you read your code right? could it be a 45 instead of 54, 45 is rich exhaust, pretty easy to mistake, i have to sit and let the code run a few times to be sure, trying not to blink "lol" hoping i don't miss anything, since your truck in not the right year for obd ll i would say this is the case since according to my book there is no code 54 for the pre' obd ll.
i hope this is of some help, let us know ok.

[2000CAYukon]

Originally Posted by strmn94

well to the first reply, the distribitor shaft is fine. as i said i have replaced the timing chain and sprokets. the shaft has no play.
to the second responce.
the way i know there is alot of fuel, is you can see the excessive fuel spray from the injectors now. never seen it before. i bought this truck new in 94.
the lope is not from a missfire. plugs, wires, cap and rotor was just replaced over the weekend. also rebuilt the regulator on the TBI unit.
the lope sounds like there is a large lift long duration cam in it, and there is not. i have been around the automotive for a long time. took auto shop in high school, worked in 2 differant garages, also worked on the funny car in my avitar for 4 years. i have rebuilt a few engines. and i have also hopped up a couple of them myself.
the lope goes away when you are running, say about 1000 rpm. it is loping at idle. bring the rpm up and it smooths out. the inside of the exhaust has a slight black build up. looking at the plugs, i can tell that it is showing a little rich on about 3 to 5 cylinders. the one thing i have not done is replace the injectors, they are not cheap.
one thing i have not tried is to clean the ECM connections yet, since I and everyone else that has driven the truck smokes.

any other ideas are welcome.

i also replaced the EGR valve and solinoid a couple of years ago.
the engine has never been overhauled. fuel filter was replaced when the fuel pump went out, and caused a back fire.

I bought my 90 new and I also have the "lope". It only happens at idle and it only happens when the engine is fully warmed up. Mine also has a slight miss that I can feel cold and when the engine is warm. This weekend, I will be looking at ECM grounds and I have been running out of ideas. Mine seems to be heat related. If I park it for 1/2 hour. The lope will be gone until the engine warms up completely.

Good luck and please post back if you figure yours out and I will post if I find anything this weekend.

//2000CAYukon

[strmn94]

well it seems that my room mate that drives it now, had someone looking at it, accually about 3 differant people. it seems that one of tem decided to adjust the timing with a timing light with out doing the things you have to do first. it is smoothed out some, but using alot of gas.
so i am going to reset the toiming, replace the ignition mod, o2 sensor, and temp sensor. i'll try these, and see what happens.
it is getting too much fuel, and i can smell it now. i just got home off the road. i only get home on the weekends.
goping to do these things tomorrow. i'll post later to let you know how it goes. it's better than taking it to the dealer, and getting charged an arm and a leg, since i also have no converter anymore.

update: replaced ingnition modual, O2 senson, coolant temp sensor, and EGR solinoid. still has the rough lopie idle. still getting too much fuel.
next, intake gaskets, map sensor, checking cam lift, and the last thing would be replacing the injectors.
this is driving me nuts.

[2000CAYukon]

The MAP may be the next step. You should make sure the vacuum line is in good shape going to the MAP. The job of the MAP is to detect engine load. Under engine load, the PCM will add more fuel and timing.

//2000CAYukon

[strmn94]

well still no good, now i'm getting codes 22 and 33. going to have someone i know come over and clean the ECM connections with contact cleaner. and then go from there. will get back next weekend when i go at it again. got to go to new york state, for tues morn delivery.
oh, also replaced the Idle air solinoid.

[2000CAYukon]

Originally Posted by strmn94

well still no good, now i'm getting codes 22 and 33. going to have someone i know come over and clean the ECM connections with contact cleaner. and then go from there. will get back next weekend when i go at it again. got to go to new york state, for tues morn delivery.
oh, also replaced the Idle air solinoid.

22 is TPS low voltage. When I replaced my MAP, I forgot to plug the TPS back in and got this code.

33 is low vacuum to MAP so make sure the vacuum hose is connected and not leaking.

//2000CAYukon

[strmn94]

well here is what has happened.
it seems that after all that was replaced, it boiled down to a stuck EGR valve.
this one person my room mate knows, came over after i went on the road.
i told him to check the vacuum and also check the ecm connections.
will he also looked at the egr adn found it was stuck open. must have happened after the back fire, but it is now running fine. replaced the header gaskets, the paper ones burned out again. went and got the good racing type header gaskets, and put them in this time. told her that the bolts need to be checked about every week for a couple of months.
but problem solved, and at least with the new sensors and emission parts replaced, should be able to get another 190,000 miles out of the old truck.

thanls all for the help.

[LOUD-ASS-SIERRA]

exactly what emission parts did you replace? i just started reading your post from top to bottom but i have no idea how old it is..when i first read your problem and heard you had ur exhaust from the headers back (no cat) i figured the o2 sensors where out of whack w/ it missing. If i am correct you have ur exhaust from headers-back, no cat, no muffler. im just wondering how does it sound? i gotta 94 sierra also, and i know you and i have reply'd to the same posts before. what made you take the cat off? i know its illegal and you can get fined a lot if you get pulled over and they check. im really just wondering how does it sound?? and when you decided to run your exhaust this way, how did your truck run the first few times without the cat and missing o2 sensors. everytime i want to do this to my truck im always reminded about the o2 sensors and ive read posts of ppl removing it and the missing sensors messing up their whole engine and what not. im sure you've gained a little hp but were there any downsides to taking the cat off and running headers back? any other knoledge about this would be great if you can. thanks

[strmn94]

Originally Posted by LOUD-ASS-SIERRA

exactly what emission parts did you replace? i just started reading your post from top to bottom but i have no idea how old it is..when i first read your problem and heard you had ur exhaust from the headers back (no cat) i figured the o2 sensors where out of whack w/ it missing. If i am correct you have ur exhaust from headers-back, no cat, no muffler. im just wondering how does it sound? i gotta 94 sierra also, and i know you and i have reply'd to the same posts before. what made you take the cat off? i know its illegal and you can get fined a lot if you get pulled over and they check. im really just wondering how does it sound?? and when you decided to run your exhaust this way, how did your truck run the first few times without the cat and missing o2 sensors. everytime i want to do this to my truck im always reminded about the o2 sensors and ive read posts of ppl removing it and the missing sensors messing up their whole engine and what not. im sure you've gained a little hp but were there any downsides to taking the cat off and running headers back? any other knoledge about this would be great if you can. thanks

well with as old as te truck is, and we do not haev emission testing stations here, i don't worry about it. it sounds real sweet. i have the gibson cat back system. i found the cat was going bad when i took the y pipe off to remove the tranny 2 1/2 years ago. i broke 5 of the 6 studs for the pipe to the manifold, and had pieces falling out of the convertor, that was when i decided to replace the stock manifolds with headers. now the ones for the 94 are shorties. i found later that there was a y pipe available from the header manufacture, but i had one made for it. the O2 sensor was installed on the left header collector. i have now moved it to as location after the y.

now here are the sensors i replaced and parts,
EGR solinoid, MAP sensor, IAC motor, the throttle position switch, cap, rotor, wires, plugs, O2 sensor, coolant temp sensor, and it all turned out the EGR valve was stuck open caused by some carbon the got stuck in it. this must have happened when it backfired when the fuel pump quit.
truck is running great now, and has lots of power again.
one good thing that happens when you remove the cat, is your mileage will improve, and power will improve.