Fluctuating idle, bucking and stalling.

kingfd · Post by **kingfd** » August 7th, 2005, 1:15 am

I have dropped in on a couple of threads and asked some questions but I think my problems warrant a new thread.

When car is started and engine is cold everything seems fine. Idle stable car normal to drive. Problems only occur once car has warmed up. Once warm the following problems show themselves

- Fluctuating idle

Unfortunately there doesn't seem to be a pattern to this. But it with move up and down from 1k to a point where it will almost stall and then shoot back up to 1k again. Other times it will shoot up to 2k and hold then suddenly fall below 1k and back up again.

- Bucking

Again when car is warm. Car will start to buck and loss power. When accelerator is pushed it will just splutter as though it wants to stall. If you take your foot off and let it coast the bucking and spluttering stops until you put your foot down again. This fault is very intermittant.

- Stalling

Will only happen once car is warm. When idle gets low enough and car stalls it will not start for at least a couple of minutes. Seems to happen more often when stopped on a hill or when clutch is pushed in.

I have searched previous threads and taken advice so far as to what could be the cause of the problems so this is what i have checked so far.

- have replaced plugs
- have replaced spark plug leads
- cleaned distributor
- checked intake lines and hoses, replaced air filter

Any other things I should be looking at?

jimishadow · Post by **jimishadow** » August 7th, 2005, 2:47 pm

compression test

kingfd · Post by **kingfd** » August 8th, 2005, 5:59 am

^ Ok I'll get it checked out.

Anyone else have any ideas?

Shades · Post by **Shades** » August 8th, 2005, 10:25 am

Check the wires on the battery... I had a similar problem but it was cause my negative battery wire was loose.

Also try adjusting your idle screw. Wait till your car has warmed up first so that you get an accurate reading. It might be idling too low when warmed up. I think stock idle is 750-850 rpm's. As long as you keep it under 1000rpms it'll be alright.

kingfd · Post by **kingfd** » August 9th, 2005, 7:33 am

^ Yeah unfortunately I have tried this and it doesn't seem to have fixed anything. When car is running without faults it is perfectly fine, like nothings wrong. Strong acceleration runs smooth and then other times all of the above faults.

I don't know really getting on my nerves. Can't trust it to drive anywhere.

nos92mx3 · Post by **nos92mx3** » August 9th, 2005, 10:24 am

Ive seen this problem on a friends dsm with the high idle, have you tried pulling codes yet?

cjthor · Post by **cjthor** » August 9th, 2005, 10:55 am

I would check your IAC valve. Located at the bottom of your throttle body. This is a common problem on the MX3.

Tunes67 · Post by **Tunes67** » August 9th, 2005, 11:00 am

Double check for vacuum leaks.. specifically the ribbed intake hose from the air box to the throttle body. Also check the grommet that the PCV valve goes into.. they harden up over time and can allow air past the PCV. If you determine that it isnt a vacuum leak.. then its probably as cjthor mentioned.. your IAC valve is probably gummed up. I did a How To on cleaning and adjusting your Throttle body, including the IAC valve.. Its a 2 thread posting.. Part 2 is in the FAQ section.. but you will need to search a bit to find Part 1 for whatever reason. Best of luck.

Tunes67

kingfd · Post by **kingfd** » August 12th, 2005, 4:51 pm

Thanks for the replies guys. I have bookmarked your 'How to' Tunes. I'll go over the intake again and see if I can find anything. If I don't I'll go ahead with the 'How to'. I'll keep you posted.

kingfd · Post by **kingfd** » August 16th, 2005, 6:42 am

Well I checked intake again and can't seem to find any evidence of splitting or loose hoses. I have removed the TB but it seems to be very different from the one that Tunes has posted in the 'How too" thread. I'll take some pics tomorrow and post them.

kingfd · Post by **kingfd** » August 21st, 2005, 3:47 am

Well as I mentioned above I have removed the TB but it is quite different. When I removed the TB the gasket which was there had almost completely disintegrated. Areas around the outside had broken away as well as there being a few cracks right through to the middle. It was difficult to remove since it seemed to be stuck to the TB real good. Anyway here is how it is right now. Still more cleaning to do.

kingfd · Post by **kingfd** » August 21st, 2005, 3:48 am

Here is the other side of the TB.

kingfd · Post by **kingfd** » August 21st, 2005, 3:51 am

This is the IAC from the top. Again you'll see it is completely different.

kingfd · Post by **kingfd** » August 21st, 2005, 3:55 am

This is looking at the bottom of the TB where the IAC attaches. I have ordered a new seal which is due in a week.

kingfd · Post by **kingfd** » August 21st, 2005, 3:57 am

Now I haven't figured this out yet but my TPS only has 3 pins instead of 4 so if you have any ideas let me know.