1993 850 RPM pulsing up and down at idle Topic is solved

Paul-93-850 · Post by **Paul-93-850** » 04 Oct 2017, 12:58

1993 850

Check engine light came on and code indicated the MAF.
RPMs were very high at idle.

I bought a re-manufactured Bosch MAF and now the RPMs pulse up and down at idle.

What might this indicate?

Post by **bmdubya1198** » 04 Oct 2017, 16:36

Is your check engine light still on? When was the last time your IACV was cleaned?

Post by **misha** » 05 Oct 2017, 12:39

Paul-93-850 wrote: ↑04 Oct 2017, 12:58 ...I bought a re-manufactured Bosch MAF and now the RPMs pulse up and down at idle.

What might this indicate?

That indicates that re-manufactured & aftermarket MAF will not work on these cars.
Only brand new or even good known used OEM BOSCH.

1993 n/a should use just an insert.

Disconnect the MAF and see if it runs better.

Paul-93-850 · Post by **Paul-93-850** » 07 Oct 2017, 23:42

Disconnected the MAF and it idles too fast.

Post by **erikv11** » 07 Oct 2017, 23:44

But it doesn't surge? Bingo - the MAF is the problem.

Remanufactured MAF will have non-Bosch electronics, and they usually (like 90% + of the time) don't work right in these cars.

Post by **misha** » 08 Oct 2017, 14:38

Fast idle with maf disconnected could indicate a clogged iac valve or a vacuum leak.
The fact that fluctuating up & down rpm goes away with maf disconnected indicates that maf is bad.
NEVER use aftermarket sensors on these cars.ONLY oem....new or good known used.

Post by **misha** » 08 Oct 2017, 14:38

Somehow my post has been duplicated.

Paul-93-850 · Post by **Paul-93-850** » 23 Oct 2017, 16:39

I removed and cleaned the idle air control and the throttle body. No apparent bad vacuum hoses. High idle speed has only dropped slightly. Still rough and hesitating acceleration. When first starting, the idle goes up and down a few times and then stays high.

Before doing the cleaning the code only showed 1-1-3 short term fuel trim upper limit.

Assuming MAF is OK, what would these symptoms indicate?

Post by **misha** » 23 Oct 2017, 16:51

Re-manufactured or aftermarket Maf CAN'T be ok for these cars.
It's better to run the car with it disconnected.
Other that...large vacuum leak somewhere like ribbed plastic hose from air filter housing,vacuum tree,pcv system,hose for fuel evaporation...
On how much rpm it is idling?
N/a idles around 900(+-50) rpm.

Paul-93-850 · Post by **Paul-93-850** » 24 Oct 2017, 21:22

RPM at idle goes from around 1200 to 1800.