Continuing on...BF on Acceleration

I have replaced all of the sensors and yesterday after installing the CTS and O2 sesnors, started the engine and immediately coded with the MAP sensor 33.

Was not able to balance TBs as I had run out of time and engine would not run with out lugging and stalling.

Will order the refurbed ECM and try it again. Had thoughts of putting the Hypertech chip back in to see if I pick up the 33 code again. If not maybe I should leave things as they are with the Hypertech...not that I care that much for that chip.

Did observe that I had that popping sound yesterday like the one that I had heard when I put in the last refurb that I had decided did not function properly, It appears to be coming from the front TB with a burst of fuel but both TBs had filters in place so I could not actually see what was going on at the same time of the noise.

T

 

Any chance you can find an ECM with the chip.Did you ever replace the MAP?

Jim

 

Jim,

Yes, MAP, TPS, CTS, and O2 all replaced and found a bad connection (burnt and exposed to ambient air) between catalytic converter and EGR pump return line that I repaired with a kit from Ecklers. Found it when I replaced the O2 sensor.

Most likely will not find an ECM with chip. But can put in Hyptech at least to see if it codes before I order another ECM. I will explore the chip thing. Maybe Wally at Corvette Generation in Dade City. (He has 4 to 5 acres of c-3s in various states of wreck with the occasional restoration). He has let me borrow a relay for testing a different issue in the past.

Will let you know.

Tom

 

have you cleaned the carbon out of the throttle bodies? look for a black ring around the butterflies.

 

Yes, carbon cleaned many times after backfires. They are clean at this moment.

 

This may have been asked before but have you replace the plenum gasket with the felpro gasket? The factory silicon always leaks, some worse than others.

 

The engine was rebuilt in 2004 and I have no idea what gaskets were used. I had the TBs rebuilt in 2007 and re-installed myself. I have no idea what gaskets were in the TB gasket set.

The car ran fine until a year ago after sitting for many months. Until I realized that my transmission had failed for a second time in 20,000 miles after a rebuild (obviously a bad one at that).

I have re-torqued all manifold bolts and checked TB mounts. I am just stalling a wee bit as I am about to start the car up again after realizing I did not install the CTS properly and did that yesterday. It is raining and miserable outside today and not really interested in being in the garage. As soon as I bring to normal idle, I will run a test drive and give a report. Last two drives as I was putting in new sensors seemed to go rather well. I have not had a backfire in a good while during any of my recent test drives.

 

Started engine to let idle after clearing computer of codes. Found a leak coming from CTS where I had erred and not tightened properly. After tightening properly, still leaked and appears to have a crack in the manifold running from the threads. Check out photo to see what I am observing. Looks like a stop-drill in the manifold in the middle of the apparent crack.

[IMG][/IMG]

 

Thats bad luck. I'm not sure how you can fix that? JB weld?

Jim

 

If it weren't for bad luck, I would have none at all.

Do have a friend who does weld aluminum. Though it does look like an old crack, I cannot attest to why it might show itself now...unless I ham-handed something.

May check with Wally at Corvette Generation on a previously owned manifold.

I may be offline for a while. I had cleared the codes and started to run at idle to temperature and it appeared to be doing just fine til I discovered the leak and attempted to tighten the CTS.

RATS!!!

 

Maybe I was a little "**** retentive" and overdid the project repair manual that I made. Copied the 21 steps from the Shop Manual and put it in a table with a box to check removed, one to mark it re-installed and a box for notes. Put all parts removed in plastic bags and labeled them. Had already taken "before pictures" and now am taking after pictures. Copied pages from the Shop manual with part names in pictures as I cannot remember names of either my tools or parts. When I have help working on this car I usually point and ask someone to give me that "thingy" tool over there...no...to the left...no...a little back to the right...anyhow my wife suggests the "AR" title...not sure why. Question: Would you want this man working on your car???

NO!

Duh!

Here is a picture of the manifold which clearly shows the burn pattern from my backfire issues (now on the back burner as I fix my own mistake by cracking the manifold).



Also, I was able to get a straight on view of the apparent crack in the manifold rather than using a mirror. It appears pretty clear that I cracked it...must have been me...



I put Teflon tape on the old CTS to see if it really leaked...it did. I have the new gasket set and a new CTS.

Hope to take the manifold in tomorrow to get it welded and then go from there.

Will keep you posted.

 

Interesting. Mine backfired in the same cylinder. I had a bent push rod. While you are at it pull the valve cover on that side and check the rod and spring. I replaced those two items.

A year or so later I did the timing chain. It had jumped a tooth.

Jim

 

All that blach soot is your egr valve my friend. That how most look but yours is a little darker for a rebuilt engine....
The easy answer is your EGR valve is not closing all the way. This will cause exhaust gas to enter the intake and the car will idle erratic !!!

 

The black soot is inside of the intake tunnels on both 1 and 2. I have experienced many backfires through both throttle bodies and have watched them as they occur. I only showed one side but have pictures that show the backfire soot on both 1 & 2.

Noted that the EGR shows some soot as well but have tested and observed the EGR doing its thing. Whether or not it is closing/opening to the stops I cannot tell you.

I am exploring options on the next move. I am ready to take the intake manifold in to be welded if it is possible and if not have a backup plan to get another manifold locally.

I am concerned that sticky valves or cam issues may also be in play. I have seen no black soot on the rear tunnels for 5, 6, 7 and 8 so have less confidence on the EGR is an issue. There is almost no soot in the tunnels leading to 3 and 4.

Oh joy! or make that no joy.

 

Took the plenum in to get it welded...nice job and finally took a look inside the intake ports and observed the valves. Remember, I only had 20,000 on this car since engine rebuild.

Valves (nearly all intake) are heavily gummed up and it appears it is even on the seat.

Have a look see even though the picture does not do justice to the amount of sticky stuff, one gets the idea. So, ham-handing the CTS did give me an opportunity to look inside and see how badly I am gummed up. I am in the process of removing the heads now and hope to be on top of that issue soon.

[IMG][/IMG]

 

The reason they're called cease-fires is because of their manifold cracking issues.

There was a guy on Bangshift.com who hot-rodded a cross fire manifold. IIRC he blocked the egr and ground the inlet off....

http://www.bangshift.com/forum/showt...e-SBC-Manifold

that is a lot of carbon on the valves.... ug

 

Wow! I have had a crossfire for 223K miles and 15 years and have followed everything I could read about crossfire and this is the first time I have heard of manifold cracking issues. Ceasefire was always related to the dual TBI's and balancing, etc., etc. Never, repeat, never heard of manifold cracking.

 

you're fortunate. There was a GM tech bulletin on those intakes. I've had the misfortune of helping 4 people who had cracked cross-fire intakes (replacing); and know of several more (including the one in the link I provided).

 

I have no experience with cracked manifolds nor do I suspect that mine is cracked...except where I cracked the threads at the CTS site. All is well with the manifold. Most followers of this thread have not heard the entire story therefore would suggest holding back on jumping to conclusions.

My car ran fine until October 2010 when the transmission failed for the second time in 20,000 miles. The car sat for nine months as I was frustrated, out of work and generally not happy as I discovered it was not the rear end that was the cause of the noise but the tranny. (Trans repaired end of June 2011).

The car sat so long that the ethanol turned bad (shellac) and I believe gummed up the works upon ignition. Not likely to give much consideration to cracks (other than the one I caused). Heads are coming off tomorrow as I have begun to loosen the head bolts within the last hour. Will start over with a good valve job. That is a serious carbon buildup on the valves and it is much worse than the picture. It is literally caked on the valve heads and stems and looks like burnt sugar. Only two valve had a semi clean appearance.

 

Maybe so. Just never heard of that and been digging around the crossfire since 1997.

BTW, I did the same thing that was documented in bangshift thread. Except I did not cut the runners back. When I did it in about 1998 or so, there was alot of discussion about if and how much, so I skipped that. But refinished my inside just like this one. Really smoothed everything and then hit it with a light spray of high temp chrome paint. Looked great at the time, but 150K miles later, just standard aluminum color.

Also did an HCL acid bath of manifold. Man did that thing put off fumes. Glad I was in the driveway. But really cleaned up the thing.