BluVudu

Have an 88 Toyota Pickup 4 cyl EFI. I'm having a problem with it not running right. When I first start it, it runs perfect but as soon as the engine warms up, it starts chugging, smoking, backfiring and popping flames out of the tailpipe. After it has ran for about 10 minutes or so, if I can keep it running, it smoothes out and runs fine but is still running extremely rich and backfiring. I have replaced as follows... battery, ignition coil, plugs and wires, distributor cap and rotor, new distributor with new pickup coil, MAF sensor, air filter, fuel pressure regulator, fuel pump. The timing is set perfect although it runs a bit better if I advance it a few degrees. I'm thinking maybe the TPS or possibly the computer or computer grounds (the engine is not original) but wanted to get some opinions. If you have an idea, please let me know. Thanks BLU you can also email me at jcd3425@yahoo.com

BluVudu

Just ran codes and got o2 sensor and TPS. I already replaced the o2 sensor so I'm lost on that one but gonna put a new TPS on and see if it helps.

CyMoN

is the check engine light on? lol never mind^

how old and what type of O2 sensor did you get.

in the shop manual it has info on testing the TPS

BluVudu

hmmm... I'm gonna have to check the specs on the o2 sensor. I'm about to see if the TPS is bad or just needs calibrated as well. Other info on the o2 sensor is I just put it in 3 weeks ago and it's the one from AutoZone (ugh).

CyMoN

I shelled out 120$ for a denso O2 sensor from autohaus.com
autozone can order a denso one but I think they wanted 140$ for it.

BluVudu

lol well I hope it doesn't come to that because rather than buy a new pipe I cut the old one out and welded the new one in. I may have to redo it though. Waiting on a friend to bring an ohm meter so I can check both sensors and hopefully see what's up. They way things have gone so far, I won't be surprised if I have to order a high quality o2 sensor because the one that I got was universal and it has me wondering if I didn't waste the money on it.

CyMoN

after you check the TPS if it is ok take back the O2 sensor if it is still under warranty.

Kiroshu

the o2 sensor would not cause this issue ur having. The o2 has very little affect in engine performance. On a vehicle this old it can really only trim fuel a few %. If you have an exhaust leak however before the o2 sensor that will cause it to run rich. so yea. TPS is possible and mostlikey since its came up from the computers stored codes. If Tps does not fixed it i would start checking compression and see if theres any vaccum leaks or intake leaks and or intake manifold leaks.

BluVudu

I checked the TPS and it is just a hair over on the closed throttle setting... the rest is perfect. Don't think that's my problem. I'm starting to wonder if there is a problem with the computer. The way it runs is very inconsistent as it will run one way and then if I turn it off like to get gas or something, when I turn it back on it does the exact opposite. I checked all of the vac lines today as well but I suppose there could be an exhaust manifold leak. Stupid question but this truck has the manifold, exhaust pipe and then a glass pack cherry bomb muffler. No cat and not connected to the tail pipe yet. Could that cause this type of issue? I've never had an issue with exhaust like that before but I am learning a lot of new things with this truck haha!

Kiroshu

Exhaust has nothing to do with it. I wonder if its your mass air flow sensor it is possible. When its running try beating on the mass air flow sensor and see if it changes. Also possible ERG problem. Opening at wrong times and or too early. Try taking off that vac line that goes to the ERG and drive it see if it changes the prob. If those tests don't satisfy you, you can.... test the computer.... do a "Computer Slap Test" If you don't already know where the computer is in ur truck, its in the pasasnger kick panel. Take the panel off and give the computer a little slap while the truck is running. If it changes the why the truck runs then ur computer is bad or just has something loose in it.

BluVudu

ok I will try the ERG. I put a new mass airflow sensor on yesterday haha... that wasn't it. And today while it was running I did smack the computer and I didn't hear any change. I was also wondering about the dashpot. When you open the throttle, should the plunger rod on the dashpot come up fast as the throttle opens or does it come up really slow? Also, when the truck is off and you open the throttle, the dashpot plunger rod doesn't move at all but can be pulled up and down. I appreciate all of this insight by the way...

BluVudu

also, when I had the pasenger kick panel off, inside the fender is rusted and has had water in it at one point. I'm gonna fill the hole now that I know it's there but it has had water sitting there before which makes me wonder if it has somehow gotten in the computer... does the computer slap test always work? lol

CyMoN

I would be Leary of slapping something if it is not the problem when they cost around 300$
would suck to break it if it where not the problem.

try testing the injectors and cold start injector

BluVudu

To be honest I'm so tired of screwing with this truck and wasting money on it that I'm about to take it to a mechanic and let them figure out what's wrong with it. Know any good yota techs in Indy? lol

Kiroshu

The computer slap test is not a 100% chance of working usually only when something really serious has broke in it does it work. But it works for the most part on older OBD1 vehicles... kinda a shade tree thing but it works. You mentioned its not the original engine are the grounds correct on it? Throttle response is supose to be fast so thats expected. usually TPS's give noticeable trouble upon acceleration. I would not think its the cold start injector... that would have alot to do with start-up and cold morning starts.... injectors possible but it sems the problem is deeper than injecters. Faulty injectors would sure cause bad missfire. how about valve clearances? it seems to me it only happens upon warm-up? If so try adjusting valves.... any codes?

BluVudu

The codes I got were for TPS and O2 sensor. I really don't think the TPS is bad as it checked almost perfect except for when throttle was fully closed, but it was just barely over specs. It doesn't do it just on warm up... sometimes yes...sometimes no but after warm up... it seems to have a mind of it's own. I let it run for probably 15 minutes to make sure it was good to go... drove 2 miles to the gas station and it ran decent there... when I got back in, it took probably 10 minutes to get it restarted and then I had a 30 miles drive to get home and it ran like crap all the way... if I was on the gas though, it ran ok. From a coast to getting back into the gas it stuttered and backfired and popped out of the exhaust. And when I let off the gas, it sounded like a quiet jake brake on a semi lol like it only had half compression. A friend is emailing me all of the diagrams for the grounds so that I can check those and also he said to open the computer and see if there's water damage inside it as the only toyotas he's ever heard of that had a computer problem were crashes and water damages... and as I said, there are visible water lines inside the fender and just below the computer so it is a good possibility.

Kiroshu

before you get into all that please try the EGR. You know where its at right? If so just take the vac line off of it let i hang there or what ever it won't hurt and see if that fixes it before you get any deeper cause it could be the very simple. ur symptoms sound like egr trouble thats why i want ur to try it. i hope ur computer is not water damaged. Usually they are sealed from all weather but its possible.... but i don't think soo especially if the slap test showed nothing different.

BluVudu

ok cool... I'm getting ready to go do the EGR thing now... yeah I know where it is but I didn't know how to test it since you can't stick your finger in and push the diaphragm up and down like the old style worked lol so I am trying to go do something tonight and I will take the vac line off and see what happens... if no change...I will stay home lol not in the mood to fight with it tonight.

BluVudu

Ok... took the vac off the EGR and nothing changed. Hopefully not a dumb question but should I have reset the computer first and then started it with the vac line off? It runs really sluggish and then the check engine light comes on and it runs smooth for like 30 seconds if that, then the light goes off and it almost dies and the idle does a slow up and down over and over for a while until it smoothes out... it keeps repeating all of this over and over but still almost undriveable. When it dies, the only way I can get it started again is to pump the gas which I was told was actually allowing more air to mix into the gas that's flooding the engine. I'm so new with EFI engines... hope I'm not being a pain but at least I'm learning things lol

BluVudu

when I took the vac line off of the EGR, there wasn't much vac coming from the line... I don't remember how much I should feel there.