So I just picked up an unfinished project a 1988 Formula and wanted to get some ideas where to start addressing an idle issue . The 305 has been pulled and a 350 is now in its place I believe it to be out of an early 90s truck . All the fuel injection (tpi) has been put back on the 350 , but when started or when coming to a stop it wont keep an idle . It is 5 speed also original to the 305 so I have to keep my foot on the clutch and keep her running . I haven’t dropped the tank but I dont think the fuel system has had any upgrades and doubt there has been any computer tweeking to compensate for the larger motor . Would these be the most likely things to address to fix the issue ? Like I said I have very limited info on the build and I dont think I will be able to get much from the person who did the swap so any suggestions would help . Thanks guys .
I would email j&j he is a pro with TPI cars
You have a scanner? You need to watch the Throttle Position Sensor, and the Idle Air Control Valve. With the engine off, key on the T.P.S. should read around .3 to .5 @ idle & up to around 4.8 at W.O.T… Numbers should move smoothly from idle to W.O.T. with #'s slowly climbing, not stopping at any one #, than jumping up skipping a bunch of #'s as you slowly push the gas pedal down. The I.A.C. should drop as the engine idle drops. If you blip the throttle (engine running) it should jump up, & as the #'s drop, the idle should follow. If the idle starts dropping too low and you watch the I.A.C. try to raise the idle by raising the numbers, it may be a bad I.A.C…
If you don’t have a scanner you can check the T.P.S. with a volt meter. It’s also a good idea to pull the I.A.C. valve and inspect the pintle. Clean it , the housing it sits in and the throttle body itself with air intake cleaner. I don’t think using carb cleaner is recommended. Being very carefull, lightly try to push the pintle in just a small amount. It should move some. Don’t go ruining it by pushing or pulling it in or out more than a few mm’s. If it is frozen in one position, there is a good chance that is the problem. There are a bunch of other things that could cause this but these are a couple quick & common problems. All this assuming the car runs good off idle, no engine miss, noises, etc. Good luck, hope it helps.
I wish I had a scanner but dont so this weekend I’ll try the volt meter . The car runs out fine for the most part . I am also leaning towards the timing being off as it just doesnt have the power I would expect and pops when you let off the gas just after really being on it , but it goes well and doesnt stumble anywhere . Thanks for the tips if you have anymore keep em coming . Thanks
Possible big ass vaccum leak, Check for that also
Do you have a check engine light? MAF sensor might be installed wrong or it could be the burnoff relay mounted to the firewall. Gotta love father/son butcher swaps. I’ll let you borrow my scanner but 1988 is still OBDI so all you have to do is stick a piece of wire to ground out one of the prongs in the ALDL, then count your flashes of the SES light. Google the code and post what it is. Heres a link to OBDI info and the ALDL diagaram: http://users.wpi.edu/~irocjay/obd.html
Some other thoughts:
-Was it a T-5 stock? If they swapped in a manual, the ECM will think you have no transmission. Pretty unlikely scenario, but possible. If you have shift up/shift down lights in the second gauge circle then it’s a stock 5 speed.
-TPI 350’s had a “dual snorkel” intake tract. 305’s had a single. This could screw with the MAF sensor if they swapped a 350 one in.
-When swapping from a 305 to a 350, you need to change the knock sensor to one designed for a 350. It should be on the passenger side of the block, I think it’s a blue wire. The knock sensor monitors sound frequency in the motor based on the rythm it should have which is directly related to displacement. This would shut you down if it thought you were too lean and detonating.
-305 ESC Modules (Electric Spark Modules) don’t work right on 350’s either sometimes. It’ll get it started and running rough but not right.
-You’re going to have to change to a 350 PROM. Car won’t run right if you don’t.
-You’ll also NEED bigger injectors. Stock ones are 22 lbs. for a 350 TPI.
I was trying to fit this into our conversation when I was cooking on friday, just got too busy. Must be nice to drive a delivery truck around all day and BS with all the master chefs in Lewiston! Might have to come down there one day and take a look at this mess for you, you buy the beer and let me park for Bills games though. Also getting tuning software for my 350 swap, so might be able to burn you a PROM this winter/spring.
Oh and avoid dropping the gas tank at all costs. Rear axle has to come down a TON and the filler neck gets stuck on everything on the way out. It’s an ugly mess. Also if it was a stock TPI car the fuel pump should be able to handle it. I want to say the pressure needed on my old 305 was the same as a 350. (45 psi maybe? could be wrong)