will the 89 MAF work in the 88 IROC?

 

Yes. 86-89 used the same MAF. Well, actually the early 86s had some burnoff issues, but if I recall that was an issue with the burnoff relay, not the MAF itself. It's irrelivant because the chances of anybody still running the OEM 86 MAF is quite rare.

You can even get away with using an 85 MAF on an 86-89 car, although you can't use an 86-89 MAF on an 85 car. I mention this because the 85 MAF seems to be a more reliable unit. If you compare it to the 86+ style, you'll see that the wire in the tube is a much thicker diameter.

 

In laymans terms:

YES

 

It's weird you posted this. My IROC is a 85, and still has the '870 ECM and stock TPI harness. The complete engine and TPI hardware are from a '87 IROC. When I was chasing down a weird backfire when I first got the car, I ended up scoring a Wells 145 MAF for a good price. I swapped it onto the car in place of the original '85 Bosch piece.

It worked FINE. The ONLY "problem" I had was that the MAF would throw a code 34 on initial COLD start up ONLY. And this didn't happen all the time. This only started after replacing the TPS , and I've read where others had the same issue.

I recently put the '85 Bosch MAF sensor back on for ****s and giggles, and I haven't seen a code 34 yet. But I am chasing a weird high cold idle problem. On a cold start, it will idle up to 1500 RPM or so, then drop down quickly to 750 RPM or so, then back up. It will do this several times when cold. After I start driving it and the engine warms up it goes away. I've going to go ahead and install a new CTS and reset TPS and minimum air today, so I'm thinking that should take care of it.

 

It's not uncommon for the idle to throttle up when cold, and bounce up and down for a while. The ECM looks for input from the O2 sensor and if the sensor is not up to temp the ECM will toggle back and forth. Before you replace the CTS you might just check the voltage setting of the TPS. I would not wast money on a CTS it probably won't help your problem. Check your IAC and its passages, its common for them to get gummed up.

 

True...but the idle itself ( after this happened ) was now higher, even when warm. Where as before I set min air, TPS, idle etc and I had it at a certain RPM..which has now increased.

And where normally the car would immediately idle up on a cold start, then after a bit drop down, it stopped doing that.


I just got done replacing the CTS. Bumped the idle just a hair, and reset the TPSv at .55 at closed throttle and I'm getting 4.25v at WOT.

I just cranked it up awhile ago..1st start of the day, and it immediately idle up to 1600 RPM. No sag, no jumping, rock steady and SMOOTH. After a bit of idling the idle dropped smoothly and gradually to @ 750 RPM in P and it idle at @650 RPM in D....still stable and smooth.

Car seems to idle much smoother all around. I'll post results later, as I'm going to test the old sensor to see what it's reading.


BTW.......IAC and TB were totally cleaned out ( off the engine ) about 2 months ago. I removed the IAC and cleaned, passages etc.


Thanks

 

That's very interresting. I used an 88 MAF on my 85 when it still had the 870 and it threw a code. I don't remember what the idle quality was like, but because of the code, I threw the 85 MAF back in. I did run the 85 MAF on the 88 for a while and had no problems.

The main difference between the 85 and the 86+ was that the 85 sent a pulsed signal to the ECM, and the 86+ used a non-pulsed signal. I had assume that the 165 ECM has a buffer on the input that is able to smooth out the pulsed signal sufficiently, and that the buffered signal was close enough to what an 86+ would use.

But for the 85 to work properly with the non-pulsed signal from the newer MAF really boggles me. It just doesn't seem possible. I never got the chance to monitor the 88 MAF on the 870 ECM with my auto x-ray before I yanked it.