Peter Bowen

Good Morning... This is a long post, but sometimes the devil is in the details...

I recently became the "caretaker" of my dad's 1988 Formula 350. Dad is the original owner and as a teenager, we had an agreement. I kept the car tuned and in top form and he would provide pocket money. So for about the first 5 years of it's life, I was the mechanic. That was great until I moved out and over the years it has had other mechanics work on it. About a month ago, it passed back into my hands and it was in rough shape. The engine has been rebuilt within the last five years, but it sat in the driveway and was driven about once a week, but over the last year nothing.

When I started this project, it had an active rat's nest and the battery was completely dead. The plenum gaskets were reversed (front was in the back and back was in the front), and the engine and bay were covered with grime and rat crap. It also had what appeared to be a small oil leak on the driver's side, dripping from the power steering box.

The reason I got involved is that it's up for California registration which requires smog. I contemplated non-op status but, you know, I know this car, so no sweat.

I charged up the battery, cleaned out the rat nest, looked at the hoses, wires, and vacuum lines, checked the fluids, and she fired right up. the idle sounded a little rough, but it has always "grumbled" and it's been 20 years, so I took it home. About two weeks later, off I went to the smog guy. In short it blew HC of almost 300... yet everything else is in line. Seems weird, but whatever - just HC. Okay, so here we go.

Fuel, Ignition or Air...

Checked codes... MAF, EGR, Crankshaft Sensor.

MAF - One of the other "mechanics" removed the MAF bracket and the MAF and snorkels were hanging free. I found a braket on ebay, sanded, painted and installed it. I forgot to reconnect the MAF harness, so it's probably that.

EGR - Hmmm - The EGR valve looks new and the vacuum line is there. The temp sensor looks old, but the wire is intact and connected.

Crankshaft - well, the engine isn't running, so probably okay - the ECM is at least throwing codes right?

Idles at 700 in park and 550ish in drive. Stable and steady. It's not smooth, but stable - if that makes sense.

Ignition - I don't know when the plugs were last changed, and the wires feel brittle ( that happens when they are leaning up against the exhaust manifold) I can also see arcing on the drivers side where the plug wires are against the manifold. Plugs are normal, although worn so the gaps are not within spec. Under close inspection, wires are in fact brittle and cracked. Replaced all plugs and plug wires and rerouted wires w/ new looms. Checking for spark, they all had strong spark. I unplugged the spark management wire and checked the timing. It's about 4 degrees vs 6, so that's on my list too - but one thing at a time. I'm also thinking that a distributor cap/rotor/coil replacement couldn't hurt, but I don't want to just throw parts at a problem.

Fuel - 42 PSI at prime. 35 psi at idle. Performed leak down test. Pressure drops immediately after prime. Clamping hoses indicated that the check valve in the pump is bad. Also the regulator is bad. Good news is that the injectors hold pressure. Whew. Replaced the regulator diaphragm. Prior mechanic lost a screw and replaced it with a 10mm long one and stripped the torx head of two of the original security screws. Ordered new screws so that I can have 6 matching screws. I also have 100 of them. Unfortunately not the security type so I won't be winning the concourse d'elegance. Still leaks down, so I'm going to have to figure out the seat. I'm also thinking that an inline check valve will help on the pump side. in any case though - probably not a cause of high HC. I also ran some fuel injector cleaner in the gas - no sea foam yet.

Air - Replaced the Air filter. Checked the snorkels for holes. Checked for MAF code after resetting computer. Cleaned throttle body. Reset IAC valve. (Have not removed and cleaned it yet)

Emissions - So with a loping idle, I figured that it was a vacuum leak. Tested the vacuum and it comes in at 15 at idle - I was hoping for somewhere around 21. It does increase with throttle up to about 2000 RPM . Most of the lines were recently replaced with the exception of the hard lines for the climate control and under the plenum. Fixed a few of the hard vacuum lines. When I had the plenum off , I took the opportunity to put the gaskets back on correctly and replace the vacuum lines under the plenum. I checked the sticker under the hood and made sure that everything was ship shape. I started the car and still 15. I plugged all of the vacuum lines at the plenum along with the pcv valve and no change. Also no vacuum at all from the port under the throttle body, although given some throttle it increases.

So it must be a difficult to find leak... I ran all over it with propane - no change. I have not tried carb cleaner or water yet (that's next - I need to pick up carb cleaner - none of my cars have a carb ) I thought maybe the inside of the intake manifold gasket may have a leak, so I plugged the PCV intake, exhaust and oil filler and the vacuum didn't improve. I'm stumped.

Oh - and I found that the EGR vacuum relay wire was unplugged. Didn't seem to help. The EGR valve isn't getting any vaccum at idle though since there isn't any vacuum at the throttle body port at idle.

I probably took care of my HC problem when I fixed the plugs and wires, but the idle still feels low and it is misfiring. I'm going to get the ALDL cable soon, so that should help with sensors, etc...

So at the end of all of that. Where am I not looking for a vaccum leak?

Thanks for any help or advice.

Fred SS

iTrader: (3)

{. . Also no vacuum at all from the port under the throttle body, although given some throttle it increases. }


That is normal. The egr is hooked to a port that has no vacuum at idle and vacuum increases with throttle opening. You do not want egr at idle. The egr solenoid pulses the vacuum signal. Also, you may want to remove and egr and clean it and the passages. Although probably not the cause of your high HC, but could be the cause of rough idle. The egr could be stuck open at idle. Good luck

Peter Bowen

Thanks for the confirmation on the throttle body. I feel better about that. I'll pull the EGR valve off when the screws for the regulator arrive and give it a good once over in the cleaning dept.

DENN_SHAH

iTrader: (1)

if you had a vacuum leak, you would have a high idle.

you mention the crankshaft when talking codes, i take that to mean code 12. ALDL jumpered, key on engine off, code 12 is a code, but not really, main thing it means is the computer system is working and able to output codes. if the engine light worked but it did not flash code 12,then there would be a problem.

paulo57509

It would help if you would post an image of your test results showing the measurements of all 5 of the gases measured.

Are all the emissions equipment visually present? Any "fails" for visual?

Peter Bowen

Sure... here you go...

NoEmissions84TA

iTrader: (1)

Check these:
EGR valve stuck open.
The diaphragm in your power brake booster could have a hole in it, creating a large vacuum leak.
A BIG camshaft got installed.
Someone incorrectly adjusted the rocker arms.

Peter Bowen

I disconnected the brake booster and plugged the line. The vacuum didn't increase.

I'll check the EGR valve when I pull off the plenum to replace the screws in the pressure regulator.

Peter Bowen

The EGR valve is a positive type, looks like I need to get the plenum back together to check it. I would feel better if it had been the original neg type, but I can't find a neg type. It looks like the positive type is the only one available. Is that right?

The archives are are full of two opinions on swapping in a positive egr valve. Which is right?

NoEmissions84TA

iTrader: (1)

I can't answer that one, but if it is leaking exhaust into the intake manifold, that will cause a rough idle.

paulo57509

Just my off the top of my feeble head....

You're definitely rich (obvious from your HC numbers). The O2% measurement just confirms this. It should show slight excess oxygen because of the AIR injection system blowing into the converter.

I don't quite understand how the NOx numbers are represented. I never seen a printout that has the "GP" columns before. IOW, what was the measured PPM? Assuming the measured PPM is represented in the AVE column, you fail here too (I'm Capt'n Obvious).

I would concentrate on mixture control; O2 sensor, leaking injectors (internal) past the pintle), pressure regulator. A vacuum leak, fooling the ECM into falsely enriching the mixture could be contributing to high HC numbers.

Don't drive it too much like this. It'll eventually kill the converter. However, I'm going to take a stab at this and say the converter is already dead (or close to it) and is no longer able to handle the NOx.

Fix the mixture problem first, confirm that the EGR is functioning and the passages are not plugged. Re-test (expect having to replace the converter) and get your sticker.

Another ....It might be in your best interest (and wallet) to have someone diagnose and pin point the issue(s) and repair them rather than going the DIY approach. There's way too much speculation here without more in depth diagnosis.

Dang, that "GROSS POLLUTER" label is kinda harsh, yes?

Edit: I have three vehicles that are getting harder and harder to pass emissions testing. The Camaro, high mileage Lumina and an ultra high mileage Acura. They will fail the first time with 100% certainty even when all the mechanics and electronics are functioning normally. But I'm still able to get them registered and back on the road.

Peter Bowen

I ordered and got an OBD1 cable, so I should be able to see what the sensors are saying.

In the mean time, I pulled off the EGR valve and cleaned it out. I also pulled the EGR solenoid and bench tested it, and it works. Since I had the plenum off and I was working on the back of the engine, I replaced the rotor and distributor cap (badly scored and pitted). I also replaced the fuel regulator diaphragm again (defective the first time) and I cleaned the IAC. I'm about to put the plenum back on.

I found that the charcoal canister is rotted, but I'm dealing with that in another thread.

I'll get it back together and see what is different.

Also - as a side note, when pulling the EGR solenoid, I lost an 8mm wrench down the back of the engine. I've run over it with lights, magnets, airhoses, everything that I can think of to find it. I think it slid down the top of the transmission tunnel, but I can't find it. Has anyone had this happen - and is there some odd pocket that I should be looking for instead of the top of the transmission? Thanks as always!

NoEmissions84TA

iTrader: (1)

AH, the black hole into "tools-never-to-be-seen-again" land.

Nope, it's never happened to anyone else - only you.

Peter Bowen

I put the intake back together last night and started it up. It sounded good... a couple of revs and clang!, it fell to the ground. I don't know where it was hiding but it is sleeping safely in the tool drawer now.

Peter Bowen

Well I cleaned the egr valve and everything seems to be in good shape. Start it and it sounds pretty good. So I thought I would use winaldl to check the sensors and things. I got the new cable, set up winaldl, plugged in the cable and fired 'er up. Blinking check engine like the manual suggested and all of the data is flowing. Once the engine warms up a little, the data is intermittent.

I'm going to start a new thread so that some poor fellow with the same problem can search and find the answer.

If the ecm gets hot and stops working correctly, that might explain things, huh?

Peter Bowen

Okay - Update.

I solved the ECM issue by buying a new ECM and building a serial cable using the two transistor circuit. I'm reasonably sure that I now have a spare ECM. I should have taken it back, but I held it too long.

I tested the injectors and I had a couple with shorted coils, so I ordered some Bosche 3's from South Coast and put them in. Once I got the scan cable build, it showed that the computer was reading lean and adding fuel... well, that would do it, so I replaced the O2 sensor. Once I did that, the BLM table was right around 128. Yay!

So I think that I took care of the rich condition. However it is still low on power and it periodically throws an EGR code.

It also threw a MAF code, so I got some cleaner and cleaned it out. Looking at the BLM table though, the data doesn't seem to be what I expect, WRT the air flow vs RPM.

I suspect that the cat may be plugged. I think the next thing I need to do is to check the backpressure and go from there.

Any other things I should be looking at?

NoEmissions84TA

iTrader: (1)

Take a second look at your plug wires. It's very easy to get #5 and #7 swapped.

Peter Bowen

Thanks for the tip... I checked the plug wires three times tonight just to be sure - then had to run to date night.

Before leaving, disconnected the maf and ifirednup the engine. The exhaust smelled rich again, but ran well. I’m going to check both relays and clean the sensor again, and go through the troubleshooting steps in the service manual again. May be MAF time.

Peter Bowen

Update - It passed smog! It was so clean that the mechanic was afraid that the SMOG police would pay him a visit for cheating. I guess when you go through all of the systems and replace the parts that aren't working, things work a little better.

gearhead141

Did you end up replacing the CAT? Can you tell us what you think was the cause? We are all about root cause analysis here.

NoEmissions84TA

iTrader: (1)

Congrats! So what was the problem(s)?

Peter Bowen

When I checked the cats (not clogged), I noticed that the silly smog valve wasn't working right. I pulled it off and bench tested it and one of the solenoids was shorted. I replaced it with one from a 'vette ($40 vs $400 for the one for my car ), but I'm watching ebay for the right one at the right price. It exhausts the air in the wrong direction, so it makes a bit of noise.

I also replaced the exhaust checkvalves and replaced the silicone tube that connects the A.I.R. system to the cat.

It still has a bit of a miss at idle, but only in closed loop. I had a friend who thought it sounded like a loose timing chain, but it's only in closed loop, so I'm inclined to think something in the ignition.