Good day. I'm new to the 3rd gen land. I am working on a friends GTA because I became tired of seeing it sit in his driveway for far too long. All he does is drive the car. Knows nothing of how to fix it. Ok. My question is. What could cause the hesitation. I push the pedal in and the rpms drop then pick up. Disconnected the intake tube just enough to let some air in and the rpms drop. I'm thinking not enough fuel. But the exhaust smells like running rich - maybe no cat, haven't checked yet. Thank you for your help.

 

You need to talk to the computer. Get some live data. Check the BLM's. Also check fuel pressure. Injectors are highly suspect on these cars as are fuel pumps. Also MAF sensors.

GD

 

Thank you.
Forgot to add a tidbit. Car sat for 2 years with almost a half tank of gas.
Fuel pressure is fine at idle with the regulator unplugged, and when just priming. I don't see a MAF sensor.

 

87 should have a MAF sensor. If it doesn't, that's a problem (or it was converted to SD but that's unlikely)

 

Ok I'll check again tomorrow. Where would it be located? From TPI it goes to a duct to a plastic box looking thing to the filter box. thank you

 

It’s in the air duct next to the radiator.

 

Found it. It's just after the air filter. Haven't checked it out yet. No codes as well.

 

Magic 8-ball says injectors. Especially if they're original.

 

I unplugged the MAF while it was running and it stumbled but kept running. Would the MAF just need a cleaning? I do believe that the injectors are the original ones. Thank you.

 

I think a video will help a lot as well. Going to try to post a link. Because I didn't mention that it's a pain to start when cold.

 

+1


old/stale gasoline, too.
Bet it’s a fuel issue, overall

 

Replace the injectors, fuel pressure regulator, fuel pump, and filter. Depending on condition also replace the tank and sending unit. Your future efforts to drive the car will thank you.

GD

 

Going to have to agree.

On both of our Formulas we've swapped all that. Exception is the injectors on my wife's 88. Theyre all good. Sub 80k mile car though. Less I touch that car the better.

 

I would lean more toward that way if when giving it gas would stay bogged but after it initially bogs for a second or two it picks up a revs like normal. May have to turn volume up. Thank you

Link:

 

As RPM increases, non-contributing or poor contributing cylinders become harder to distinguish and less important to sustaining engine operation. At lower rpm a few cylinders can make a huge difference.

Ultimately we are only guessing and you need to find out what the computer is seeing from its sensors. MAF, CTS, TPS, O2, etc. The computer is the gatekeeper - if you don't consult it first you are just going to run in circles and troubleshoot with Visa - likely without much success.

GD

 

I put Lucas fuel system cleaner in the tank mixed it up with gas. Let it run for 20 min. Let sit for an hour. Started it up and the hesitation was less. Will check again after a night of sitting. If the hesitation is still less, then clogged injectors it is. Thank you

 

You have to be careful with those fuel system/fuel injector cleaners. If you have a gunk in the tank or debris in your lines....the cleaner will loosen it and it will flow right into the injectors which will
cause them to either leak or clog up
Check the resistance on them while you're at it

 

The stuff didn't change anything. Gonna pull some plugs and see what is going on. I don't have the ability to talk to the computer.

 

[QUOTE=southbay08;6336580]You have to be careful with those fuel system/fuel injector cleaners. If you have a gunk in the tank or debris in your lines....the cleaner will loosen it and it will flow right into the injectors which will
cause them to either leak or clog up
Check the resistance on them while you're at it[/QUOTE]


+1 for THIS.

Step #1 for any TPI hesitation/stalling/starting issue w/ original injectors, period.

 

had a similar situation with my car and it wound up being a bad pump, then after i replaced it the pulsator in the tank had ruptured (was my fault for installing one with a walbro pump). I could hardly get it to idle, it would backfire and sputter, and if i could baby it up to red then it would take it. I see you have good fuel pressure when it is idling. that would happen to me too, but the main clue was the immediate drop down after i shut down the motor.

 

Now that you mentioned it. It reminded me of my issue with my Camaro. But that was with a slit in the hose just above the pump. I'm not dropping the tank to get to the pump. Way too much involved for a car that isn't mine. Hell too much involved for my car. Lol. I cut a panel above the tank. Now my Camaro runs beautiful. The pressure gauge does go to 0 after I shut it down. Thank you

 

https://www.thirdgen.org/forums/tpi/...hold-fuel.html

go to post #5 for the leak down test if it is dropping to 0 psi immediately

 

Followed the link. According to the step by step. It turns out that the pump is bad. I clamped the feed line after the pump primed and pressure held. After I released the clamp the pressure dropped like a rock. I'm guessing if the pump doesn't hold pressure after shut off, that would cause the starting and running issue that I have. Thank you

 

Honestly, that isn't really any indication of anything. A lot of pumps these days do not have check valves, so they do not hold pressure after the pump turns off.

This is because the line pressurizes in under 1 second.

What is your fuel pressure at? That is the most important metric. If pressure is good during startup and cranking then do not fret if there is bleed down (that is confirmed not to be a leaky injector)

 

This is a meaningless test. Modern turbine pumps don't check the pressure when they are off. Pressure while running is all that matters.

GD

 

Then why does the pump need to prime? Also the Haynes repair manual says that it needs to hold pressure. I never heard of fuel injection not needing to hold pressure in the lines after the pump shuts off. You need pressure in the lines after the pump primes so the cranking doesn't take too long. The pump could be the issue why the car is hard to keep running at first as well, because the pressure keeps dropping after each attempt of starting. Did a complete leak down test. No pressure loss except for when pump shuts off. Thank you

 

a)its someone else's car
b)you are not willing to do anything that's recommended by the very people you ARE ASKING FOR HELP(that is foolish)

my advice to you either a)buy it and fix it properly or b)ignore it,let it rot and have someone
else deal with it.i sure as hell wouldn't throw 5 minutes of time or a nickle into
someone else's car who was unwilling to at least attempt to repair it himself.

 

The only thing that I can't do is talk to the computer. As I mentioned before. When someone says that basically it doesn't matter if the fuel pressure holds or not and no other research proves it tells me that the source isn't reliable. I mean no disrespect. At the start I said that I was new to 3rd gens. It doesn't mean I'm new to working on vehicles. I just don't have the scan tools and such because I don't make a living off of fixing automobiles. For the fuel pressure part. I had someone turn the key to prime and I crimped the feed line and the pressure reached its max. Then started the car. It started with no problem. Then did it again without crimping and it took a while to start again. I did the leak down test and nothing leaked until I uncrimped the feed line. Means bad pump. If that doesn't fix it 100% then the injectors will be next. Once this is done I'm washing my hands of this car. Lol. If it was my car it wouldn't have gotten neglected.
I do appreciate everyone's help whether the advice helped or not and made sense or not. Nobody knows everything. Especially me. Thank you again.

 

Changed the pump. Holding pressure after pump stops. Starts much better. Still has the hesitation. Injectors are next but that is next year. Thank you everyone for your help in this mess.