HIGH ENGINE IDLE

1988 Chevrolet Blazer

Tiny

4uzindian

January, 1, 2012 AT 10:11 PM

1988 s-10 blazer 2.8 was idling at 1100 rpm for long time. Decided to try a new iac valve. Also got a new tbi gasket. Installed them both now the idle is at 2000 rpm. Is there any thing I could check besides bringing to a shop so they can test using there equipment

18 Answers

Tiny

rasmataz

January, 1, 2012 AT 10:32 PM

Did you clean the IACV port and throtttle body-also look for a vacuum leak

Tiny

rivermikerat

January, 1, 2012 AT 10:32 PM

Check idle adjustment. Check cold start valve.

Tiny

4uzindian

January, 2, 2012 AT 3:37 PM

I cleaned tb and checked for leaks. Lines are old though i'll probally replace some of them. To rivermike rat. I don't think ther is an idle adjustment screw on this tbi unit. I don't know what or where the cold start vavle is or how to check it. I did this monday morning I took out new iac checked it was no more than one and one eight inch from base. I put the washer on, last post it was off. Turned the key to on for 10 seconds then to off. Started and it idled at 1500. Then I pulled the connector on that plug that screws into the manifold in front of the tbi unit. To my suprise the idle went down to 1100 rpm right where it's been for the last 4 years. Should I replace this sensor (what is it).

Tiny

rivermikerat

January, 2, 2012 AT 7:28 PM

If I'm thinking of the right sensor, it's the manifold absolute pressure sensor. Check the voltage in this sensor. At idle, it should be lower than at higher RPMs.

Tiny

4uzindian

January, 2, 2012 AT 11:34 PM

That sounds easy do I unplug the connection and put the probes into the connector?

Tiny

rivermikerat

January, 2, 2012 AT 11:45 PM

No. Keep it connected. Probe the back of the connector.

Tiny

4uzindian

January, 5, 2012 AT 10:43 PM

Itryed the voltage test, tihs is how I did it. The red lead from the tester to the white wire on the connector. Black lead from tester to black wire on connector. The voltage was higher at raised throtle than at low. I stuck saftey pins into it to do test. The sensor has a white and black wire coming out of it. Did I do these the right way?

Tiny

rivermikerat

January, 6, 2012 AT 4:48 AM

Yes. And it appears the sensor is working properly. I've asked a colleague for some help.

Tiny

4uzindian

January, 6, 2012 AT 11:33 PM

I'm going to put a new iac valve in on saturday.I'll post when I get it done.

Tiny

rivermikerat

January, 7, 2012 AT 12:25 AM

Ok.

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