I've read many posts on this problem, and it seems like it's very common with TPI cars and there can be many, many causes for it. I've got a 87 305 TPI 5 spd, injectors were serviced about 5k miles ago, new EGR valve, new TPS, new IAC and clean IAC bore and throttle body, new 02 sensor about 3k miles ago. Also just set min. idle RPM per instruction found on this site. I also just put coated hooker 2055's on and it ran fine for about 1 week after.

The problem is worse when the engine is cold and the engine almost stalls when I shift gears, but other than idle hunting the car runs pretty well once it's warmed up. No stalling or other stumbling problems when warm.

With the IAC disconnected it still surges from about 500 to 900 rpm. No change after re-connecting the IAC. With the MAF disconnected the car runs rough at idle, but does not surge.

Am I to assume this conforms that the MAF is bad?

 

Heh heh heh! Be ve-e-e-wy quiet. I'm hunting idols. Wook out, Idol, I'm gonna bwast ya...

If the idle hunts with the IAC disconnected, you can safely presume you have either a vacuum leak somewhare, or a fuel mixture/ignition problem. If the engine doesn't stumble ot "hunt" with the MAF disconencted, the ignition system is probabaly O.K. The extra rich mixture that is the default with a sensor disconnected (Backup Fuel and Spark Mode) could be masking a vacuum leak somewhere.

A MAF car should run with the MAF disconnected, albeit on the rich and sluggish side. One thing you can do is test the MAF output with a digital voltmeter. At a fixed RPM, there should be very little variation in output voltage:



If the MAF has been altered (de-screened) or the intake dusctwork is leaking, or the PCV valve, EGR valve, or brake booster is leaking vacuum, the MAF output may wander a bit. A breather-type oil filler cap will also cause poor MAF readings.

Before you condemn a MAF for wandering output, you should also verify the voltage supplied at the 'E' terminal of the MAF with the engine running. Any variation there can contribute to poor MAF function. Reliable grounds at the 'A' and 'B' terminals are also essential.



You may indeed have a failing MAF, but your problem is not typical of a MAF failure mode. Have you tried tapping on the MAF housing with a couple of fingers (Tap test)while the engine is at idle to see if it stumbles?

 

Ok Elmer---err---Vader The MAF is not de-screened or modified in any way. I'm not willing to open that can of worms up just yet The MAF was replaced maybe 10 years ago, but never modded. I also have not tried the "tap test" yet. This is the first I've read about it, and beleive me I've read a lot about TPI on here.

I'll try the tap test, and as soon as I figure out where to get voltage from, I'll measure the MAF idle voltage and post it.

Remember, I'm a machinist and heavy mechanic, not much of an electronics guy, but am trying! With the help of others here, this thing hasn't beaten me yet, and I'm not about to start letting it do so now

 

Most machinists are fairly meticulous. If you can hand countour a decent circle on a manual mill, you'll have no problems with the electronics. The difference will be in the tools.

A reasonably priced digital multimeter is about all you'll need for most auto electronics.

 

I have a mulitmeter, just got to figure out where and how to pick up the voltage reading from the "E" and not screw something up. The terminal at the MAF sensor is hard to get at, so I guess I'll have to follow the wire back from it a bit and poke a small hole in it to get a reading.

By the way, the "tap" test did nothing to the way the engine ran.

And, I'm a CNC machining type of guy. I've got a manual mill, but it's used for support for the CNC's.

 

wel, on a lighter note, just tell your buds that its that crazy cam u installed, thats what i tell them (week ignition on start up, i think i need new ignition system.)