Replaced IAC valve and now engine doesn't run right

chuckyuen

chuckyuen

New member
I replaced my IAC valve and spark plugs with Autolite Double Platinum plugs to correct a problem is was having with the car idling rough when cold and dying at times. Now the engine idles nicely but when I floor the accelerator now it goes strong initially and then just bogs down and loses power. What did I do wrong? What do you guys think is causing this? Maybe bad spark plug wires? Help please.
 
chuckyuen

chuckyuen

New member
Re: Replaced IAC valve and now engine doesn't run right

Ok, swapped the plugs with NGK ones and the car rims much better. Though it's still not accelerating quite as strong as it used to and it doesn't shift as hard from 1st to 2nd like it used to. Did I somehow screw up the computer? Do I need to reset it or go through some kind of reset process? Also does the IAC valve automatically adjust itself or do I need to do something to it? Sorry for all the newbie questions and thanks in advance for the help guys.
 
SY2932

SY2932

Administrator
Re: Replaced IAC valve and now engine doesn't run right

Here's some IAC stuff from my manuals:





However, you current problem doesn't *seem* related...
 
chuckyuen

chuckyuen

New member
Re: Replaced IAC valve and now engine doesn't run right

Do you guys think new spark plug wires would help? Right now there are MSD wires on there, but they were very hard to remove and now when I put them back on, a couple of them don't "click" on anymore. They slide on, but don't really click on when I push on them. Thanks again for all the help.
 
chuckyuen

chuckyuen

New member
Re: Replaced IAC valve and now engine doesn't run right

So I was tinkering on the truck tonight after driving it a bit and noticing that it seems to miss every now and then especially under load. And when I pop the hood open, I hear a rapid ticking noise coming from the engine. To me it sounds like one of the plug wires is arcing. The truck didn't do this before I changed the plugs and IAC valve, so I'm thinking that I must have messed up the wires when I changed the plugs. What do you guys think?
 
D

dogboy

uk typhoon
Re: Replaced IAC valve and now engine doesn't run right

try a complete ingnition service, plug wires, cap,coil, rota arm then you can be half way certain that it's not that also replace ALL the rubber vac hoses as you where in that area/areas and they are a shit if thay leak
 
sleepy

sleepy

Member
Re: Replaced IAC valve and now engine doesn't run right

With it going strong and then losing power, what does everyone think about maybe a fuel problem? When was the last fuel filter for you? Do you still have a stock pump or what aftermarket is in there???
 
chuckyuen

chuckyuen

New member
Re: Replaced IAC valve and now engine doesn't run right

I just bought this truck 3 weeks ago, so I'm not sure how old the fuel filter is, or what fuel pump is in there. It does have an aftermarket fuel pressure regulator that is blue. Sorry, I'm kind of a newbie and not very technical.
 
powercat6

powercat6

Active member
Re: Replaced IAC valve and now engine doesn't run right

chuckyuen said:
I just bought this truck 3 weeks ago, so I'm not sure how old the fuel filter is, or what fuel pump is in there. It does have an aftermarket fuel pressure regulator that is blue. Sorry, I'm kind of a newbie and not very technical.
Click to expand...

Post the last four digits of your VIN and what model year it is. Maybe someone on here knows your truck.
 
SYO237

SYO237

SyTy Registry
Re: Replaced IAC valve and now engine doesn't run right

A blue AFPR usually is a Kenne Bell. Change the fuel filter, it takes all of 10 minutes, you'll need 2 wrenches and something to catch (preferably not your face or mouth) the small amount of gas that will come out. It located on the driver side, inside the frame rail about the halfway point on the frame. Silver canister, cant miss it.

If your wires are not "clicking" back on the plugs, you might want to consider replacing them. If the clip gets pushed back into the boot of the plug, it will never make good contact...usually a miss is a good indication of this especially if it happens right after you do plugs. Taylor Spiro Pros seem to be one of the most preferred wires.
 
G

GM TURBO

Sell Out
Re: Replaced IAC valve and now engine doesn't run right

Get your ignition straightened out first. If the wires aren't clicking on the plug - they aren't connected. If you hear arcing - they aren't connected. The last thing I'd want to do is mess with fuel around arcing ignition components.
 
chuckyuen

chuckyuen

New member
Re: Replaced IAC valve and now engine doesn't run right

Ok, replaced the wires with Taylor Spiro Pros and they definitely click on much tighter than the MSD's did. I haven't had a chance to drive it since I have the wheels off to get new tires put on. But when I hold the brakes and push the gas like I'm boost launching it, it does bog down like it did when driving at WOT.

The truck is a 91 Syclone and the last four of the vin is 0884.

If there is anyone here in Hawaii that could come take a look at it in person and help me I would gladly compensate them for their time.
 
chuckyuen

chuckyuen

New member
Re: Replaced IAC valve and now engine doesn't run right

Ok, so got the new tires put on and took it out for a test drive and it behaves the same way it used to with the MSD wires. It also backfires every now and then when I go WOT. What do you guys think?
 
JAY

JAY

Donating Member
Re: Replaced IAC valve and now engine doesn't run right

Did you reset the computer after you installed the IAC?
 
chuckyuen

chuckyuen

New member
Re: Replaced IAC valve and now engine doesn't run right

Out of desperation I unplugged the IAC valve and took the truck out for a drive and it doesn't bog down at WOT or backfire. I'm thinking that the IAC valve must be defective. Gonna swap it out for a new one and see what happens.
 
V

V

Donating Member
Re: Replaced IAC valve and now engine doesn't run right

Have you inspected the wires of the IAC with the truck running? A faulty connection at the IAC could give you headaches. Checked for vacuum leaks? Are you monitoring fuel pressure as you approach WOT?

Email or PM me if you want any help.
 
SY-1193

SY-1193

Active member
Re: Replaced IAC valve and now engine doesn't run right

chuckyuen said:
...so I'm thinking that I must have messed up the wires when I changed the plugs. What do you guys think?
Click to expand...

This may not be your problem...checking it wouldn't hurt though. Spark plug wiring sequence on a cap compliments of Richard Lee:

http://www.whitetyphoon.com/firing_order.html

I recommend replacing your distributor cap/ rotor yearly also. Use a brass terminal cap. Aluminum terminal caps degrade much quicker in our trucks.
Check your module wires while you have the cap off for corrosion and good contact (two wires going to the plastic thing that is under the rotor).

Also a good trick to remove the rotor using the McGuard wrench you should have for removing the center cap locks as a pry tool:

http://www.whitetyphoon.com/removing_rotor.html

chuckyuen said:
...Do I need to reset it or go through some kind of reset process? Also does the IAC valve automatically adjust itself or do I need to do something to it? Sorry for all the newbie questions and thanks in advance for the help guys.
Click to expand...

The IAC position is learned by the ECM at speeds above 30 mph. I would reset the ECM by removing the two fuses for 5 min. and reinstalling them then take it for a test ride to let the computer learn. Vary loads and throttle, turn on acessories and your lights all to let it learn all the differences..sit at idle and turn your steering wheel to the extreme to have the power steering pump pressure on the engine...all ways to help the computer learn. There are different designs of IAC valves -- make sure you have the correct part number. Read the two pages that Mike Campbell (SY2932) posted and follow them.

chuckyuen said:
...Now the engine idles nicely but when I floor the accelerator now it goes strong initially and then just bogs down and loses power.
Click to expand...

Ok...something else to check...You have an adjustable fuel pressure regulator, correct? Check the vacuum port on top of the regulator for gas in there. If the diaphragm inside leaks it will pull fuel into the upper part of the regulator and let the engine run ok at lower rpms and increased load but when you have higher rpms and load it will act up. You can also place a mini-vac vacuum tester on the vacuum port and see if it holds pressure.

chuckyuen said:
So I was tinkering on the truck tonight after driving it a bit and noticing that it seems to miss every now and then especially under load. And when I pop the hood open, I hear a rapid ticking noise coming from the engine. To me it sounds like one of the plug wires is arcing. The truck didn't do this before I changed the plugs and IAC valve, so I'm thinking that I must have messed up the wires when I changed the plugs. What do you guys think?
Click to expand...

This could be the injector pulses. If your fuel rail is a little tight on the injectors it may be louder on your truck than others. It sounds like a sewing machine as described by some. You may not have noticed it before because now your brain is in "WHAT IS WRONG" mode and your are suspecting everything! Check your wires for arching but it is probably just the injector noise. One other thing this could be is a leak in the exhaust manifold but I doubt it.

Good luck...don't get frustrated just keep checking things...
 
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chuckyuen

chuckyuen

New member
Re: Replaced IAC valve and now engine doesn't run right

Ok, did a reset on ecm. Drove it around under all different conditions, WOT, cruising, ac on and off, lights on and off, and it was still acting up at first, and even died off on me a few times. Then after about 10 miles of driving, it starting running really smoothly and strong.

That was a few days ago, and I took the truck out today and it starting acting up again. I finally got TTS Datamaster installed on my truck, and one thing I do notice is that the most boost I get out of the truck even at 50% TPS is 4.3 psi. Is this normal?

How many miles does it take for the ecm to reset itself and relearn everything?

Anybody want a free trip to Hawaii to tune my Syclone?:lol: I'll pay your airfare out here, you pay your own hotel and get my Syclone going strong. I'm halfway serious about this, if someone is seriously interested.
 
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