Low idle 550 rpm

[ezbeinsteezy]

I have a low idle that just doesn't seem to go away I've done everything I could think of changing the air filter, fuel filter, iac, iat, cleaning the egr valve checking vacum lines it's drive me nuts what else could it be it doesn't die thankfully I don't have a maf sensor since it's a 95 what thinking is the injectors, intake manifold gasket or timing chain any input would be great

[97cargocrawler]

What are you using to determine the rpm? A scan tool or some aftermarket pod gauge? I think stock rpm is in that range. I boosted mine up a bit (around 615) to keep the engine happy with my huge alternator, 4 electric fans and constant use of the a/c. I used a programmer to do that.

[ezbeinsteezy]

I bought a tach and it seems fairly accurate the reason why I think it's low is because it has a rattle like in the steering wheel it's nothing to do with the drive train and it's very minor but most people that ive talk to said that it's a little low. Is your idle really smooth at 600?

[sfeaver]

I looked at a tune from a 98, which is the earliest I have, and its lowest idle is 600 in neutral ac on or off, 650 in drive. 95 is probably similar. a V8 has 550 as its idle in gear. Engine warmed up.

If your seeing 550 on your scan tool, will it show you what the desired idle speed is? That will tell you right there if you are looking for a problem that isnt there!

[chevymaher]

This has been talked about before. It just depends on what they did when they built the van,. One guy got a new PCM and it was 650 rpm. And he had 550 originally. Mine has the goofy 550 deal in it.

They do like the higher idle better tho. I manually turned the idle screw up on mine without changing the computer. It idles at 700 in neutral. And 550 in gear and with the air on. But even that made a big difference in the way it acted. The extra air all the time. I mainly did it like cargo for the A/C to actually be working while it is sitting idling in parking lots in the summer. Heater works better to because it ia pumping hot water better in the winter idling.

[Coaster]

i have 2 different prom for my 95, both from 95 astro/safari.

the astro prom idles at 500 and 550 in gear/neutral and the safari prom idles at 600 and 650 in gear/neutral. astro prom shifts late, lockup at 48 mph. safari shifts early, lockup at 41 mph.

astro prom shifts way better. safari prom idles way better.

[sfeaver]

I'm curious what else is different between the two proms.. Have the calibration ids handy? Maybe I can look it up if I still have the info..

[Mmusicman]

I bought a tach and it seems fairly accurate...

"Seems accurate" based on what?

FYI: gauges (of any sort) are typically "less accurate" at the very bottom of their scales. Your's may be fine...but I'd check your OBD to be certain. Even then, it would need to be decided if the reading is normal anyway.

..the reason why I think it's low is because it has a rattle like in the steering wheel..

One thing you may have overlooked is that the idle may be fine... but the motor-mounts may be shot. It's a VERY common problem. They are "typically" good for about 150K.

My mounts are blown in in my 2000.. and it makes the idle (in gear) feel rough, shaking steering wheel... neutral smooths out, even though the rpms actually stay the same. New mounts can make your van feel like new again.

Here's the idle on my 92... which is set to about 1000 rpms...
On one occasion it dips down to 800 or 900 and almost stalls.. mounts are new.