Hello all this is my first post I’ve been lurking on here for a bit but now that I am getting deeper into working on my pickup I figured it’s time to make an account.

Ive been working on getting my family’s custom stretched ‘88 Pickup V6 back into good running shape as it has been neglected the past few years since my grandparents are too old to drive it now. It has 360k on the clock and it still drives pretty good for the most part but the main problem I have with it now is it will randomly run really bad when starting. It seems like its running rich. It will start and then sound super choppy almost like its going to die then you have to rev the piss out of it and some smoke comes out then after about 20 seconds of that it idles fine. It does this probably every other time when starting it. It seems to do it hot or cold doesn’t matter. It also doesn’t seem to matter if i let it sit after running or let it cool off or let it sit for a few days it will still do it when it feels like it.

List of things I’ve done so far: replaced fuel filter, replaced spark plugs, wires, cap, and rotor. Checked compression, checked air filter, checked cold start injector, have been running injector cleaner though it for about 6 tanks or so. I have a gut feeling it’s the injectors but I’m not sure why. Also I have a check engine light that comes on for about 30 seconds here and there and then goes away. It never stays on. I’m pretty mechanically inclined but I don’t even know where to start on this one especially since there are so many emissions systems on this engine. Also its throwing me for a loop that I can’t seem to reliability duplicate the problem so that makes it even harder to figure out. Hoping someone will have some insight on what to look for, thanks in advance!

 

Is it smoke or steam when you start it? 360k on the clock, could be the head gasket on # 6. My 88 4tr 3.0 did the same thing.

 

It’s smoke I can smell it it’s definitely just running rich. I also did a compression check and it all came back good not sure if it could still have a bad head gasket. Also it’s super random it’s like just whenever it feels like it that’s what throws me off.

 

Spitballing here... rich means excess fuel, so I'd lean toward looking at the possibility of a sticky injector.
Not sure if the fuel pressure regulator could cause this issue as well. Injectors sound more likely to me.

 

Do you know how to check for codes? Most of them will set a "history" code, which could give you some insight.

While you could have a stuck injector, it sounds more like you're missing on one or more cylinders (the unburned fuel that goes through the cylinders that don't fire will make you think it's "running rich.") If you can replicate the rough running, you can do a "cylinder efficiency test"; pull the plug wires one at a time. If you pull a plug wire and nothing changes, that cylinder isn't firing. Then put the inductive sensor of your timing light on that plug wire; if the light flashes, the plug is firing.

[Keep in mind that the unburned air will hit the O2 sensor. The ECU will try to compensate by increasing injector open time -- actually running rich. If it hits the limit, it will set a too-lean code, which could go away once that cylinder starts working again.]

 

I don’t know how to read codes on this thing but I do have the manual and I think my dad said he knows how so I’ll try that. If I could replicated the problem that would be ideal to try I had to do that with the timing light on my land cruiser. Now that you mention it does act exactly like one or more cylinders is not firing.

Also for the check engine light for whatever reason when it’s doing it’s thing and running bad the check engine light doesn’t come on. It only comes on if you’re just driving around and it’s always running fine.

 

Yeah I keep thinking it’s the injectors I’m not sure why. I’m trying to see if there’s anything else I can look into before having to pull the intake plenum but I’m probably going to have to soon.

 

I’ve replaced the spark plugs, wires, cap and rotor. Is there anything else that could cause a intermittent misfire?

 

Well today the check engine light came on for longer than usual and then the truck died when I pulled out of a street and would barley start back up. If I’m doing this right I believe I have code 22 which is engine coolant temp circuit from what I’ve found on google. I would guess maybe a faulty temp sensor is making the truck think it’s cold when it’s hot or vice versa and maybe a faulty sensor is intermittent.

I also happen to have a huge factory service manual for my truck along with a Haynes manual and none of them tell me how to read codes I had to google it. Unless it’s called something other than check engine light or engine codes.

 

Check the section for the EFI system. The how-to starts on page FI-22. The code numbers and their meanings are on pages FI-25, etc.

Does that help? you'll need the super special; test jumper. VERY pricey item. Might cost a whole 1/2 cent for the paper clip. I made one with a 1/4 male spade terminal at both ends, and about 3 inches wire in between. Very easy.

Have fun
Pat☺

 

Thanks I found it in the manual. Also I think I must have the fancy tool for this


Installing a new water temp sensor today so we’ll see if that fixes my problem. Only odd thing is that the check engine light only comes on when it’s running fine not when it’s running crappy.

 

I see you went for the really pricey test jumper. Good, good. You get what you pay for after all...

When you replace the temp sensor, make sure the threads are good and clean. Don't use anything on the threads to prevent leaks. Like RTV, or teflon tape. The threads on the sensor AND the engine have to be clean of all foreign materiel.That's where the temp circuit gets it's ground from. Thus, any foreign substance can change the values of the sensor's resistance, causing a false reading to be detected.
So, make sure the ground from the head to the firewall is in good shape too. Then, of course, you must be sure the ground strap from the fenderwell to the battery, which is the ground for the body in general, is in good shape. Finally, naturally, the battery negative post and the terminal that connects to it must be clean and shiney. Bear in mind that the acid mist that comes out of lead/acid batteries can get inside the insulation of the wires connected to the terminals, if they aren't heat shrinked. The acid can corrode the wires inside the insulation, making for a bad cable, that is visually in good shape.

Once all THAT is squared away, read out the codes. It's a good idea to clear them first, and then, once the CE light comes on, you know the codes it's indicating are valid for your current problems. You don't want to read out an old, stored code that misleads you into chasing a problem that doesn't exist any longer.

Finally, and I really, truly mean no insult by this question, are you replacing to temp sensor that feeds the ECU, or the one that feeds the gauge on the dash? They are two differen't sensors, in two different places. I just hate to think you go to the trouble of changing what you think is the sensor feeding the ECU, and the problem doesn't change at all.

Good luck, and keep us up to date on how it goes!
Pat☺

 

Thanks for the advice but I already changed it a little while ago haha. I did change the sensor that goes to the ECU not the sender to the gauge. I was actually going to put thread sealant on it but I ran out so I put it in dry but I guess that was pure luck lol.

I haven’t checked my grounds too carefully but recently I did clean the battery terminals. If the problem persists I will look closer at all the grounds. And I did reset the check engine light and confirmed there are no codes saved now. I’m going to drive it around for a couple days and see if it comes back or if the actual issue comes back and I’ll report back here either way I hate when forums dead end.

 

Well it’s been a couple days and so far so good. Check engine light hasn’t been back and it hasn’t struggled to start at all now. Time to take it off roading this weekend! Thanks for everyone’s help🤙

 

I'm glad it's going well for you. I hope it stays that way for a long time. Have fun boonie-bouncing!
Pat☺