pr0k

I just bought my 93 Red touring last Saturday from a forum member here and I'm having some rather peculiar issues with it. Both the previous owner and I spent a week sending PM's back and forth about it, and spent 10 hours working on it today. We're both stumped on this issue so I'd like to hear from some FD vets.

When the car is completely warmed up and I've been running it (very easy driving, mostly under 3k RPM) for about 15 minutes (20 minutes on a cold night) I start to see very low vacuum and low idle accompanied by lots of popping from the exhaust. When I first start the car and blip the throttle to bypass the accelerated warmup I'm seeing about 18" vacuum on the Autometer gauge and it stays at 18" when it settles back down to 700 rpm (the needle is a touch above 700).

Boost seems fine, but I haven't put my foot into it lately. Since the PO was with me tonight and he a smart cookie when it comes to these cars I went ahead and got up to about 7psi once but not enough RPM's for the secondary turbo to spool. The engine is certainly strong, and no hiccups while driving it other than the occasional 3000RPM stumble, but even that's pretty minor.

The problem is after about 15-20 minutes of light driving the vacuum starts to drop from 17-18" at idle with no electrical or A/C load to about 14" (but still holding the 800rpm idle with the lights on), then just 3 or 4 more minutes and the whole idle situation turns to crap. Coming to a stop at a stoplight with the car in neutral, lights or no, the idle fluctuates between 500-600RPM's, the whole car starts shaking, lots of backfiring (popping from the exhaust) and vacuum drops to 12", then between 9-10". At this point I have to keep RPM's at 1200 just to keep the engine from acting up. When I'm holding it at 1500RPM's or so, I'm back to seeing 18" on the gauge.

Right before I noticed it getting bad, the vacuum would actually fluctuate between 14 and 16". That just seems odd that it would go back up right before things start to go sour.

Mods and a general overview of the car would probably help. The car itself has 46,600 miles on it, and about 5k on a Mazda reman engine from Malloy Mazda installed by the PO. The car is very stock for the most part. Here's a list of what's been done to it.

Racing Beat 304 stainless dual tip catback
304 stainless downpipe
drop in K&N air filter
silicone vaccuum hose and viton check valves
semi-polished aluminum air seperator tank (AST)
semi-polished upper intake manifold (UIM)
Exedy clutch

The trouble with this one is despite these problems, the car starts up just fine the next day and has no symptoms of leftover problems. This is definitely a heat related problem as even when the car is warmed up (before the 15-20 minutes) it runs like a champ. Today we checked the air pump, hoses for leaks, cleaned out the intercooler and changed the spark plugs. Took a good deal of the front engine bay apart (http://img138.imageshack.us/img138/3...c003403wm.jpg/). Didn't see anything glaringly obvious though. The PO thinks it's running to rich (despite the mods which would lean out the mixture) and the downpipe was slightly glowing after tonight's very mild run with little idling that could allow temps to rise much more. Unfortunately I don't have a water temperature gauge but should a downpipe be glowing after a mild run at night with 45 degree ambient temperatures? It also looked to have some white residue on it, but I don't see a whole lot of coolant hoses in that neighborhood so we had no idea where it was coming from. Didn't see any more of it after the drive tonight.

There was also a small pool of coolant that we found the source of after taking off the undertray. It was coming from a hose connected to the lower part of the radiator and did not manifest itself after the clamp was tightened. It's possible there's still an air pocket somewhere in the cooling system but would that be causing idle problems after 15-20 minutes of operation?

The only I remember him saying we didn't cover were the EGR valve, removing the UIM to see if something wasn't buggered in the rat's nest, and possibly something with the thermowax. If you guys have any ideas, I'd love some help on the issue. I can get better pictures if they're needed. Thanks.

HobbeZ

tps

Matt Hey

We thought of the TPS amongst a long list and I have heard of them getting out of adjustment or going bad but I haven't heard of them having heat related issues. Does the TPS develope problems after heating up sometimes?

pr0k

Bump for great justice.

tsmysak1

Ok, I have had some similar things happen, although not exactly as you described.

By your mods, I am assuming the intake has been off at least once. This is a sure way to pinch hoses underneath the manifold. I have had mine off twice and both times, not gotten the hoses right which has led to problems similar to yours.

Check the check valves. Make sure they are in correctly. Make sure that no hoses are off. Some are under pressure and some are under vacuum.

Check all vacuum lines and look for pinch points. Inspect carefully the AWS circuits. Look for hoses that may be collapsing when they warm up and become less stiff.

Check all the ends of the vacuum tubes. A bad hose can be a couple of psi on the gauge. Look for a broken solenoid.

Plan on spending three or four hours to do this right. You gotta get right down in the details or you won't find the problem. And when re-installing the intake, you have to make double sure that you are not squishing any hoses underneath.

My two cents...

dubulup

check fuel pressure regulator and solenoid.

pr0k

Thanks, I'll give these suggestions a shot. I probably won't be able to get to this until this weekend, so if anyone else has some ideas, I'd love to hear them. I'd like to have a long list of things to check at once so I can get this car back on the road and actually enjoy it.

RobTheBankz

I have the same problem as you have. Have not found the problem
The heat comes realy fast too. Well i hope some one know what it can be so we can sleep better at nights

PS: I get my water temp and A/F running soon, so i can se if there is something strange there.

charliegt

Download the factory service manual if you haven't already. That will help you test all of the sensors. I had problems with hot starts and running rich and it turned out that my turbo timer had crapped out.

-Charlie

RobTheBankz

What turbo timer do you have and how can it make a problem like that ?

pr0k

I don't have a turbo timer installed so I hope it's not that.

I ordered the workshop manual a couple days after I got the car, it's already come in handy. Which sensors should I be looking to test?

I only tried to start it up once after it stalled and I had to hold the starter longer and give it a little bit of gas but it still started. Is this what's considered a hot start?

The reason it doesn't die at a stoplight is because I hold my foot on the accelerator to keep it at 1500rpm's (with my left foot on the clutch, left hand on steering wheel and right hand on parking brake/shifter, good times).

pr0k

I had a curious thought on the way to school today regarding something I did to the car. I ran the car with the coolant cap off and the throttle body coolant hose disconnected. Absolutely retarded, I know, but in my mind I was combining two procedures into one (checking for bubbles in the coolant and the yellow funnel procedure to get air out of the coolant system). Needless to say, coolant shot out of the throttle body hose and all over the the right side of the bay.

Is it possible some electronics were damaged in this incident? I wouldn't think too much of it being an electonic problem as the car consistantly runs fine for the 15 minutes I described but I don't want to rule anything out. I know the MAP sensor got soaked along some other things.

Bad_Karma7

TPS voltage will go up with heat, that is why you calibrate your TPS after engine is fully warmed up.

94blkFD

check your water temp sensors, sometimes the sensor goes bad and the car will act fine. But then when the car warms up the bad sensors won't be able to read the temp and the car will run very rough at idle and sometimes even dies. You'll have to rev it up to like 3k, well at least that's what I did. And then seems to be fine again. I change the temp sensor and it never have again.