NC928S4

I don't yet own a pistol but I want one now! I don't want to wait 7 Days I'm mad now. Doh!

After replacing plugs, wires, rotors, distributor caps and coils I continue to experience low idle speed(300RPM) after she warms up. I followed JimR's GT loss of power thread and Sean's resolution. I spoke with Roger regarding connections of hoses to MAF about how they can affect performance. I was really hoping I had screwed something up during fuel line replacement. Sadly, all connections look secure although unclamped and yet I have low power(hesitation) when starting out. I did a compression test a month ago and all was good.

Help!

Bill Ball

So, it runs well cold, but has low idle and low power after it warms up. How about the temp II sensor? it may be open circuit on the LH pin which would cause a very rich mixture. I would find somebody that has Theo's diagnostic device and software or just read the resistance of each of the two pins on the sensor versus ground after the engine warms up. The resistance falls with temperature and should be 200-300 Ohms when the engine is hot. Another possibility is a MAF that fails when hot. If you can disconnect the MAF plug once the engine is warmed up and restart the car and it runs no different, that's a strong clue.

Also, have you looked at the ignition monitoring system relay LEDs when this problems happens?

NC928S4

Thanks Bill. I’ll be working with the areas best wrench to sort this out as I am getting in over my head.

Idle is good when cold but engines stumbles a little getting going even in 1st until RPMs climb. No RED or GREEN LEDs on the Relay.

SeanR

Just to make you feel better, my car, at times, will idle at 250/300 for no reason that I can find. Power is still good but occasionally that idle will just drop down like that. It's annoying to me since I can't seem to figure out why it is doing so. I do know it is not related to the ISV to boot hose and the ISV bench tests fine. Wish I had a better idea.

Mongo

What about grounds for LH and EZK at the rear of the motor under the fuel regulator and dampener. How do those look?

NC928S4

Thanks, will check tomorrow.

I ohmed out Temp II Sensor across posts and was 0 when cold and 0 at normal op temp. This looks suspicious and will order part went Frenzy completes.

I did tweak transmission cable to relax tension by 2 turns. This improved idle at op temp a little(+75-100) from 300rpm. Putting car in neutral raises idle RPM to 550-650 when at op temp.

I fear I'm searching for a ghost with this low idle issue.

the flyin' scotsman

The Temp II sensor is a dual sensor and has to be measured to ground. With the DVM on resistance/ohms red lead on one of the posts and the black lead on a good clean engine ground measure the values at various temps then repeat for the other post.

another way to measure the temp II over various tempertures it to emmers it in an ice bath and slowly heat the water and measure away.

The idle higher when not in gear tells us theres an issue with the LH to sustain correct idle speed as the eprom for an auto transmission car has software to compensate.

NC928S4

Looks like Temp II Sensor is hosed. When at Op Temp 14.85ohms on right blade to ground and 0Ohms on left blade to ground. Will order new unit on Monday.

I noted some slack from pedal to throttle cable and tightened 3 turns to make it taught. Idle is now 550-600rpm vs 250-300rpm at Op Temp. Not sure if this is the proper way to fix low idle but car is definitely running better. I no longer stall after a hesitating start stop and engine responds faster.

Also, there was a general consensus at my hometown PCA Club Octoberfest, that my CATs are probably getting clogged which is contributing to low idle and lowered power. I’m considering swapping a buddies current X-pipe setup to test against my car but that is a lot of dirty wrenching. Beers will be drunk to decide. Ultimately, I want X-Pipe and will do CAT and 2nd Muffler delete as soon as bank account can handle it.

nc_growler

Nice bit of diagnostic work Larry... Better than buying a gun...

You need to do some serious driving when the car gets roadworthy!

blown 87

If it does come down to a pistol, I suggest a .357 Remington Maximum, 125 grain at about 2400 FPS will do it, go right through the block unless you hit the crank.

Get a Dan Wesson, that way you will have six tries.

Bill Ball

Your reported results are strange. Low temp II resistance would make the car too lean when cold, causing cold start problems, but not have much effect once the engine warms up. Maybe I'm wrong. The S4 idle is electronically controlled, so a loose cable would not lower the idle. Tightening the cable enough to pull the throttle off the idle stop would raise the idle and might pull it into cruise mode (trip the idle position switch).

rdisney

He didn't say the gun was for the car!

RFJ

May I suggest a 44 mag dan wesson? have practiced on cast iron blocks,works good,Ray

NC928S4

I’m at a loss and the low idle was almost becoming a hazard as it caused occasional stalls. The tightening wasn’t much but it basically simulated me keeping my foot on the pedal to keep the idle up. And yes, Idle is supposed to be controlled electronically but the base idle settings have the Idle speed too low. It’s like the base position is off.

The levers on the throttle body did have some play on the stop(idle position) where I could hand push the throttle assembly a very little bit counterclockwise which lowered the idle. Giving the throttle clockwise to rev engine and then releasing would have the lever go back to it’s idle position but not as far as I could manipulate it by hand.

We are working on getting a few owners together to go in on a SharkTuner in the next week or so and will keep it with our Area Wrench.

Thanks for your thoughts.

worf928

Does your idle switch work? Check the connection at the LH and EZK pins. If you don't know how to check it: you'll need a multimeter and the instructions in my PPI guide linked in my sig.