Idle and gas mileage suck

[87mefull]

Whenever I start my car up it idles fine for a second, then the idle starts racing until I put it into gear. It aidles rough when sitting at a stop light or oscillates from too low to high also. However, its not consistent, it idles fine sometimes so it probably shouldn't be a vacumm leak. I've replaced the coolant temperature sensor last week and I didn't have any problems until today. Gas mileage is also down again, I only get 50 miles average to a quarter tank of gas even with mostly easy driving (cruising at 45-60mph).

I've also changed the sparkplugs, the cap, the rotor, the wires, the EGR position sensor, replaced some vacumm lines going into the EGR valve, fixed the timing, and cleaned the EGR valve also. I did all of this about 3000 miles ago but I haven't replaced the PCV valve yet.

[mrltd]

TP sensor. ....Also check for other vacuum leaks. Also, when you did the timing, did you unplug the spout connector?

[83tc]

mine did the same thing, unplug the idle air control, if it smooths out the idle speed then thats the problem, that and adjust everythin you can on the cfi unit, worked for me, runs sweet now, as for gas milage, thats normal for the winter, these cars suck on gas

[87mefull]

I took it to a friend's garage to do the timing since I didn't have a timing light. He fixed it back in early January and the car ran smooth with an average of 18-20mpg. I might check it again though since the car seems to lack a little bit of power when its not running on 93 octane.

Also, before I changed the CTS sensor, the car would surge even after you took your foot off the gas when in park for a couple of seconds instead of dropping back to idle right away.

[mrltd]

You shouldn't be wasting money on 93....

I'd double check the timing and check the TPS sensor and set the TPS.

[89LincolnTWNcar]

join the club........lol. I gots rough idle in drive and I get about 12.3 in town with a little expressway thrown in. Somethin's up with my car though cuz I have to floor it to get it to start, but it always starts up.

[nitroracer]

If you have to floor it to get it to start I think you have a fuel problem? Are the injectors good? Fuel pump & filter?

[gadget73]

89:
Sounds like a leaky injector to me. WOT starts in an EFI car are for flood mode. Do you get a blast of smoke out the tails when it fires off? I do remember the fuel pressure was dropping off pretty quickly on your car so maybe one of those pintles is jammed. Run some fuel system cleaner through it and see what happens.

87: Check for vacuum leaks. Did you reset the ECM after replacing the coolant temp sensor? I had to do that on my car to make the idle surge junk go away completely.

[87mefull]

87: Check for vacuum leaks. Did you reset the ECM after replacing the coolant temp sensor? I had to do that on my car to make the idle surge junk go away completely.

Just reset the ecm today (unplugged the battery, stepped on the brake pedal, reconnected the battery) but its still having problems. It ran really rough when I restarted it after resetting the ecm, almost stalling out several times. Then it just idled normally rough when I drove it around for 5 minutes after that. Didn't hear any vacumm leaks but I will check it again. I'm going to take it out tommorow so it might be better then.

It did get good gas mileage today (20mpg combined city/highway) and the idle wasn't racing like it did yesterday. It was really warm out today though.

There might be a problem with the CTS though, I checked the coolant and its very dirty and brown. I never changed it since I bought the car and it looks like its years overdue for a system flush. My dad had similar idling problems on his 99 Cherokee relating to the CTS (couldn't stay running on cold mornings, poor gas mileage), all he did was change the coolant and its been running fine in cold weather since then. I plan on changing the coolant this weekend.

[gadget73]

Might want to pull that sensor back out once you flush it and clean the goop off it just to make sure.

[87mefull]

Fixed part of the problem today since I flushed out the entire cooling system. It had alot of air in the system since the radiator was at half its capacity and the coolant was dirty too. Before I changed the coolant today, the car could not idle at all, it would just bog down really low and then raise the rpms to try to idle or just stall itself out. The car runs alot better now and the idling problems are getting better also.

The car still has some problems idling, its still rough when you first start it up or when your trying to park at 0-5mph. Idles fine at a stop light though, but the gas mileage seem like its still poor (only did short trips in the city though). Power varies too, it was very strong when I put gas in it today along with stp gas treatment, but later on as it got cooler is started to lack power.

I noticed one thing though, I ran the car while it was low on gas (about 1/8th left) and it was letting a decent amount of water out of the tail pipes along with sounded like a good miss or backfire. It only got worse when you hit the gas, but there was no white smoke or other signs of a blown headgasket.

After I filled it to a half a tank with 87 and added some gas treatment, it ran and drove like a bat out of hell. Didn't have any water drip out of the tailpipes since then either. I guess there is either too much condensation building up in the gas tank or it just had really bad gas in it.

I'm going to do some more work on it tommorow and change the oil probably also.

[89LincolnTWNcar]

WOOOOOOOOOOOOOOOOOOOOT!!! I was installing my passenger's Flowtech header today and I decided to check the spark plugs to see if the engine was still running rich (like it did when it had that vacuum leak). I pull # 2 out and it is fouled and is damp with fuel. Then I check 1,3, and 4 and they are all in perfect dry clean shape. SOO in other words injector # 2 is BAD. Thats why my fuel pressure drops off so quickly, thats why i have to floorboard it to get it running. I'll be replacing that soon enough. Anyone else who has a similar problem should check their plugs.