Thread: RPM's bounce while coasting

0215121959.3g2 - YouTube

I replaced the IACV as from google other cars had this problem and that was the case. Now instead of it going to 1800 is just goes to 1500, then to 1100 then back to 1500 etc until I touch the gas again. Doesnt do this at idle, just when I am driving then let off the gas and coast. Never did this until I installed the overkill pcm and AL104's. I havent shipped the stock computer back yet, if its really worth the test I can swap it and see.

Only codes that have popped up are PO131 and PO171. I got silicone lines comming to take care of any possible leak and a aeroforce comming also.

Put the stock pcm back in, that stopped the rpm bouncing while coasting. In neutral while coasting it sits at 1600rpm, normal or not? (40mph). It also seems the car rolls REALLY good in neutral or overkills pcm unmasked a problem. SO maybe stock pcm doesnt allow the bounce, but overkills allowed it to bounce. I dont know how to explain it. Ill try it this way, overkill pcm decel the rpms bounce, 1100rpm would what I would assume would be the normal neutral/coast? As with the stock pcm it is not, and I bet I could coast twice as far with the stock vs overkill pcm..

And my start from stop acceleration is greatly better with the stock vs overkill...... Overkill it seems I need to get the rpm up more before it really gets going....

Going to clean the tbody today and attempt the egr delete then throw overkills pcm back on and then see what she says until the vac lines come, perhaps tmw.

If you put the car in neutral, it's the same as being parked. Unless it's super cold..there's no reason for the idle to be that high. I'd check the TPS.

Cleaned tbody, maf and have new silicone vac lines on, nothing. I did break a tab off the I think what is BBV solenoid so I RTV the peice of broke off and put the vac line on the nipple above it, dunno if thats gonna cause problems. On the list now is to replace TPS and that solenoid thing. Then pressure test the exhaust and see if anything comes out. If its the rear header, who wants to make money!

Oh also got home from the gym today, reversed it into the driveway put it in park and the rpms were going from 600 to 1000. Did that aobut 6-7 times then leveled out and stayed normal. Couldnt reproduce it. 6 weeks til I blow the car up if I cant solve this.

Scan gauge came today. No time tmw, lots of work and gotta fix the fuel pump on the business truck! LOVE IT

Replaced tps, gonna order the bbv solenoid tonight if I remember. Ill update tmw night if it did anything. Hopefully this weekend if I remember I can pressure test the exhaust to see if there are any leaks and if there is pray it isnt the rear header.

Vac leak?

No and I went ahead and replaced them with silicone lines no difference. A new IACV knocked the rpms from 1800 to 1500. Tonight will be the new TPS test. Updates of that in about 3hrs.

WHen I put my stocker back in it doesnt bounce, I just got a 1600rpm idle when moving. Ill update tonight about the new tps. Hopefully the overkill unmasked a problem and didnt create one. I emailed will to see this thread but he must have died.

Lol this is really odd. I had the exact opposite thing happen to me. I had the same RPM bounce problem when coasting until I installed my Overkill PCM.

Possibly the timing.

Jumping from 15 to 27.

15 doesnt generate as much torque as 27 does.

At those engine speeds, 27 is right around peak torque.

Tps didnt do ****.

While putting gas in the tank 20min ago (yes I leave it running) the rpms started going nuts, from 600 to probably 1200+. I turned the car off, finished fueling restarted it hit a 1200rpm for 2 seconds then was normal.

I know I messed up the bbc solenoid and I cant go past 1/2 boost on the stock computer gauge thing also. Thats prob my fault since the vac line is now on the atmosphere line haha.

is that the part I broke the vac line off and rtv'd?

Originally Posted by cameron92

I have the exact same problem as this and come to think of it, It happened after I installed the overkill pcm.

Im going to try putting my stock pcm back in and see what happens.

Originally Posted by ITHURTZ

WHen I put my stocker back in it doesnt bounce, I just got a 1600rpm idle when moving. Ill update tonight about the new tps. Hopefully the overkill unmasked a problem and didnt create one. I emailed will to see this thread but he must have died.

oh lordy....now i'm terrified of the overkill tune i ordered this past tuesday.

Idle went to **** bouncing from 500/600-1500. Unplug the maf and it stopped. Swapped the stock pcm in. No bounce, smooth idle stable rpm's.

Before I swapped pcm's I had po102, po131, po171,po332, p1571. I deleted them all so we will see what the pcm tells me this week. 4.5weeks til emissions and all I am doing is falling down a hill.

I think aeroforce said I might have hit 2psi in boost. Gotta wait for my replacement bbv solenoid before I rule out my own ****ing up.

I just wrote things down with the stock pcm at idle after driving around. No idea what it means or if it even relates to anything but this aeroforce is interesting.

All at idle
Maf .63 lb/m
Maf frequency 2355
Throttle volts .35
Ignition Advance 22degrees
Short Trim b1 .0
Long trim .0

I did the 02 also but I wrote on cardboard with a big marker and cant read it haha. I got something that was moving inbetween 25-55

Today is going great so far. Drove it 6 miles not a DAM problem. Acceleration (throttle response) is 10 folds better with the stock pcm vs overkills. Not a hiccup, bounce even when putting it in park and letting it idle. Got some codes back

P0131 gonna be messing around with that this weekend. Got a new o2 comming, extension and new bungs, gonna relocate to test.

p0403 EGR
p0405 EGR no **** its gone

P1571 EBTCM I am sure. SO right now no p0171 is up. Excellent day today so far.

My idle in/g? or whatever that is is 19.1-19.4.