Boy, if that doesn’t sound now like with carbs, faulty accelerator pump. Req’d extra shot of raw gas along with any increase of air velocity. Cars would hesitate and falter for a few seconds with hard speed up/downshift for going faster. Translated to today’s cars, Hanky has the best plan on that I’d say. The throttle body butterfly self adjusts for cold start, acceleration with gas pedal, fuel enrichment pulse duration of injectors. Hand chokes worked perfect as long as you didn’t forget to push them in after warmup lol.

Everything is different today but the same I guess you can say. Even TV’s now a days. Still use my 50 year old rotor (like new), 30 year old VHF/UHF antenna (on roof), amplifier and of coarse big digital TV set. Picks up free air signals- way too many channels and doesn’t cost a cent. The rest is free streaming via Amazon Prime, works for me. Won’t have cable or satellite, could never recoup the costs?

oh too, the switch from 80MM to 84.5MM throttle body on my Boss Mustang works exceptional. Power gains, haven’t noticed a lot; wasn’t expecting to, all old news anyways.

 

Hey Hank thank you. I did double and triple checked the IAC per the instructions in the manual the pintle was under 28mm. it would not move out to 28 but since the instructions said nothing about being under 28 I thought it was ok as the learning would move it in and out. All three I tried including the last one in the car were all AC Delco from Rock Auto. Any more advice welcome.

Since I replaced the ECU last night and ran the train per the GM instructions it ran ok last night. This morning it was hard to start and ran like crap and every time I tried to put it into reverse it stalled. When I finally got it out of the driveway and put it into drive it was racing again but settled down as soon as drive engaged. it also stopped stalling when I put it in reverse once I drove it to the end of the street and back. Running short on Ideas on what to look at again the fuel rail pressure is 40PSI and it holds. Wondering if it is a clogged injector or two. The car is 29 years old with just 60,002 original miles thinking when they started it the first time it may have swallowed a load of junk and the screens are toast. Do you have any thoughts? 3.1 Liter V6

 

Hey Rich, I too have a 1990 Mustang LX ragtop 25th anniversary edition that runs like a top with the 5.0 got just 80,000 miles on it, wishing the Buick was as easy to work on as my pony.

 

Very nice EDQ, a few come and go by every so often and this one green fox body.... running very strong, hear him coming from 1/4 mile down the road, he’s running some horsepower.

 

Ok, an update and a question. I rechecked all the vacuum lines still can not find a leak the throttle body on top has the connection for the three main vacuum lines the rubber plug looks a bit worn so I tried some permatex ultra-black on the three plugs to see if they were actually leaking air. But no real change. I did double-check fuel pressure but I am a bit concerned about what was up. When I first put the gauge on it this morning I got zero reading no pressure I turned the key to on and got 40PSI steady from the pump. I turned it off and watched the gauge for an hour and it lost about 1 PSI. The car still runs like crap on startup and after it settles down has a solid hesitation when you go to give it gas then all is fine. Got me scratching my head not sure where to look. Car mileage sucks and you get a whiff of gas right after you start it but nothing on the cardboard I put under the car last night. I did put a new AC Delco fuel regulator on it 2 weeks ago new fuel pump in the tank and a new fuel filter. Any suggestions on where to look next would be greatly appreciated. One last thing if I disconnect the battery run the car in drive till the fan turns on and cycles off then shut it down restart and do it a second time the car runs much better till it sits overnight next day the same old racing and stalling.

 

Thanks, Hank will give it a go and let you know.

 

Hi Hank,
Followed your instructions to the T. When I turned the key back to the off position with the IAC still plugged in but not mounted the plunger shot all the way out. I was able to get it back in without a lot of effort. I did the procedure again but after it set I unplugged it then turned the key off and mounted it. What do you think IAC may have been damaged I ordered another The car was hard starting but finally she stayed running ran it for 15 mins through 3 full cycles of the radiator fan about every 4-5 mins she would stutter but never stop running. After 15 mins I shut it off and restarted the rpms jumped at first and she bucked a bit but settled down to 1000 RPMs and steady still high but down a lot from the 1800 rpms she was cranking out on startup. Never touched the gas. Any thoughts?

 

I may have given you some inaccurate info on installing the IAC.

I believe it should have read , the pintle should extend out about 1 in. and if more, lite pressure can be used to push it in to that dimension, then install it. It is not recommended to plug or unplug the IAC with the key on.
After installation, turn the key on , don't attempt to start the engine, then turn the key off. This step is supposed to allow the IAC to reset . Then start engine and allow engine to settle down to correct idle speed. Shut down engine and restart it should come to the correct idle speed.

If there is any way for additional air to get into the engine like a vacuum leak the IAC will have to account for that and set accordingly. but in the meantime the result will be a high idle speed. It might be a good idea to check for possible vacuum leaks.