Car runs better with MAF unhooked

[gsgnnut]

I went through this same problem on my 87 this spring. Drove me nuts. Almost torched the car over it but stuck to it and figured it out. I had a number of problems but it seemed my biggest was vacuum leaks. I had several loose intake bolts , egr leaked at idle, and maf hose had pin holes and oddly the maf had two holes in it where it would normally be bolted if you had a stock air cleaner. Fixed all the leaks, a tt chip and a new o2 and it has since never ran better. I also added a pvc restrictor valve and a new maf hard pipe. The vacuum gauge told the story. At idle it was fluctuating from 17 to 12 and stalled and was miserable at idle. Idle now is stable and shows 15 to 17 and is glass smooth. I do have a header leak that caused the factory chip to make it run terrible but the tt chip is open loop at idle so its a non issue for idle quality. Scanmaster numbers are very helpful in fine tuning. I would try another maf if you can and make sure the iac passages are. clean. The tips is a scotch high and as others said you should have more than 0 iac. Good luck bud. Been there and its not fun but stick with it.

 

[1984 t-type]

Would a bad intake gasket or plenum gasket do this ? If so I will change them next.

 

[gsgnnut]

It could but I would rule out all other possible causes first. Check the torque on the intake bolts and if ok leave it alone if loose snug it down.

 

[gsgnnut]

It could but I would rule out all other possible causes first. Check the torque on the intake bolts and if ok leave it alone if loose snug it down.

Also make sure the egr isn't leaking from the gasket ,diaphragm or pintle. The 1 bolt egr is a bitch to seal and they all are junk .I have a new one never used that leaked by the shaft. I made a metal block off plate and put it under the valve. Don't need it with the tt chip. Problem solved.

 

[1984 t-type]

Yea I have a block off plate. Intake bolts are tight. Can't find any vacuum leaks running out of options

 

[gsgnnut]

What is the vacuum reading at idle?

 

[1984 t-type]

Don't remember will check tomorrow. Unhooked it when I was chasing down leaks

 

[1984 t-type]

What's the go/ no go range

 

[1984 t-type]

Once up to temp idle fluctuates between like 650 and 1300 and the vacuum follows. Getting a reading of like 5 on the low and 13 high

 

[gsgnnut]

Way to low. Should be about l7 at idle. Looks like A massive Vac leak somewhere.

 

[1984 t-type]

Picked up a new intake gasket yesterday, gonna change that out after work today and see if that solves the issue.

 

[gsgnnut]

I am by no means a TB expert but I'm not sure that's going to do it. Have you checked all possible vacuum leak sources? changing hoses isn't enough you need to confirm each actuator or vac device is not leaking vacuum. A mity vac hand pump is an invaluable tool for this. an alternative Some folks do is to simply block and cap all vac lines off the plenum block to rule out leaks but I like to check every device separately. Also I would try a different MAF before pulling the intake . Also did you readjust the TPS below .46 ? as that's too high. Your last post indicated that the IAC setting was not set correctly right? how many threads are showing on the air valve adj screw? about 1-2 threads should show on the left side of the boss. Every adjustment of the air valve requires resetting the tps. I've been where you are now and it was a combination of multiple vacuum leaks AND an improper IAC setting , but at its worst my vac readings were fluctuating between 16-10 between the idle surging so it seems you may have a bigger vac leak. good luck!

 

[1984 t-type]

I have blocked off all ports on the vacuum block and used a mighty vac on each metal line none of them have leaks or made a difference when blocked off. Bought a refurbished MAF from Earl Brown he says he test them on his car before selling them so I just assumed it's ok. Checked MAF pipe and up pipe, all couplers are brand new silicone pieces with new clamps, air filter is new, rubber vac lines are new. Have reset and adjusted the IAC and TPS multiple times and both sensors are new, just about every hose and sensor on this car was bought in the last two weeks or over the winter and have less than 200 miles on them, I know that doesn't mean much but I say that to say I have physically touched and inspected just about everything on this car that can cause my issues based on what I'm reading on the forums. I'm going to go borrow a compressor and make a cap with a air fitting to go on the turbo inlet and pressurize the system to see what leaks I find, will hold off on the intake gasket until I can get this done.

 

[whitehot1]

I reset the iac again earlier and I can't get it within 20-30 range. Actually it all over the place, sometimes it's high others its at 0. For what it's worth the sensor is a new AC Delco and even when it ran good I could not keep it steady.

Did you measure how far the tip of the pintle was from the gasket on the IAC before installing it? It's not to exceed 1 and 1/8'' before installing it. Also after installing it run the engine for 1 minute and turn it off. Restart the engine and let warm up to normal operating temp then adjust it if needed,i like to let it idle and settle out on it's own before i do any adjustments to it.Make sure the TPS stays below .46 while doing adjustments on the IAC, i usually set it at .38 and then reset it to .42 key on engine off, after the IAC is set at 20 to 25. Also make sure the passage is clean in the throttle body where the IAC pintle seats into.

 

[1984 t-type]

I did not measure it before install, didn't know about that. Could I have damaged it

 

[whitehot1]

I did not measure it before install, didn't know about that. Could I have damaged it

You could have damaged it by not measuring before installing. You could take it out and see what the measurement is and if it's less than 1 and 1/8'' it should be ok.

If you do need a new IAC valve the best price i've found is on ebay. I have one of these installed on my engine and it works great.In the parts stores they cost $48.00 with tax. Here is the info for them.

IAC valve
brand name: Standard
part number: AC1
ebay item number: 291385171890
price: $9.25 shipped
location: Miami,Fla

 

[1984 t-type]

Well found 1 issue. Made a pressure tester for .39 cent and borrowed a compressor. Everyone should have one of these

 

[gsgnnut]

That's a pretty big vacuum leak! Explains the low vacuum. Think you found your problem.

 

[1984 t-type]

Yea hope so. Thanks to everybody for the help I was ready to give up on this thing lol. This tester is great also, just keep raising the pressure till u find a leak fix it and repeat.

 

[1984 t-type]

Ok if you make one of these spend more than 39 cent. My makeshift tool just let loose at 20+ pounds and scared the sh** out of me !