DuoDS

I finally got my LS1 sand rail out this weekend after 13 months of building the rail from scratch. But now I have some trouble, I think.

I have a 411 ECM that was reprogrammed and harness rewired for me. At idle the engine purrs like a kitten, but on the first run up the hill the SES light started blinking. When I came down the hill, it stopped.

I didn't take the engine over 3,000 rpm, or do anything but a very timid test-run. The engine didn't even get very warm. Then I went back to camp. Tried it again later, blinking started again on the way up, stopped when I turned around a went back down to the bottom of the hill.

Engine seemed to run strong the entire time, didn't even hiccup, didn't shake, or feel like it was missing, so I am kinda stumped here.

I read the SES codes today, and the only one the ECM had stored is P0507. But my code reader is kind of a POS, so I am not sure I completely trust it.

Any ideas here are welcome - after 13 months in my garage, I would like to have a little fun before the dune season ends for the winter.

bczee

iTrader: (12)

If you search for Thread or the FAQ in the PCM/Tuning Section. you will find many threads on this code. P0507 = Idle Air Control Higher Than Expected

most seem to be Vacuum related.

Check for vacuum leak, the IAC and it connetions. As well as the related sensors (MAF, TPS, PCV, that are around the TB or intake.).

Good luck. keep us posted.. like to hear about that Buggy flying once you get it corrected !

BC

DuoDS

Thanks, a vacuum leak is a distinct possiblity, I guess a leak-down test is in order.

However, I though the blinking SES lihgt meant something else. Reading through old posts and searchng this forum I have found that the blinking SES light usually means my engine is misfiring.

Do I have two issues here (misfire and vacuum leak) or am I just worrying too much?

bczee

iTrader: (12)

Yeah.. the Blinking SES is usually related to misfire. but I was just replying with my findings on the P0507.. you might have two problem or they might be related. Fix the known problem 1st. and maybe the other will resolve themself.. Get a good scan of the engine.. it well help.

DuoDS

Did a quick leak-down test and I didn't find any vacuum leaks using either carb cleaner or ether.

Where to search next?

DuoDS

Could a mis-fire happen and not set any codes in the ECM? I find that hard to believe.

Pop N Wood

iTrader: (1)

Sure you don't have a loose wire/connector/short to ground somewhere?

Marky522

iTrader: (8)

A blinking CEL means something is happening that can damage the CAT's, typically caused by a misfire, BUT could also be caused by a lean condition. I would diagnose your P0507, I would smoke check it personally. Make sure you have the vac connections on the very back of the intake blocked off.

Mark

bczee

iTrader: (12)

The early Gen III engine had a bad oil problem with the design of the PCV System. Excessive oil being sucked into the intake can cause misfire.. look in the intake and see if there is excessive oil in the bottom of the intake.

DuoDS

I am pretty sure there are no shorts to ground or other wiring issues. All wiring is new, and I have double / triple checked it many, many times.

PCV system is gone. Driver's valve cover piped to the passenger's and a filtered breather in the oil fill hole.

EGR is gone and plugged as well with a freeze plug and silicone.

All other vacuum lines plugged except for a small one in the rear of the engine that goes to my TH400

DuoDS

I will try a smoke test tomorrow. I need to find something to generate smoke and adapt it to the intake.

DuoDS

I dicovered today that my fuel pump could be bad or weak. Could this be the cause of my issue?

dpd069

iTrader: (1)

When I first build my sandrail, I had just fab'd an aluminum tank for it. I'd cut all the pieces and given it to my brother to weld. After one dune trip, it would start to miss when I'd put power to it in a bowl or climbing. I opened up the pump and it was full of aluminum filings. I cleaned it out best I could in the dunes and nursed it back to camp. Changed the fuel pump and it worked a charm, but I started having problems on steep hills. Eventually I had to put in a half gallon tank with about 18" of head above the fuel injection pump fed by a high volume low-pressure pump with a 'rock catcher' filter that continually recirculated back to the main fuel tank. Works great. BTW - I never hooked up the SES light so I don't know if it threw any codes when the fuel pump was weak

DuoDS

I have a spun aluminum tank with the FI pump right below it. I thoroughly cleaned the tank before installing it. Before the FI pump I put an high volume, inline fuel filter. This part of the system is 1/2 rubber line. Then after the FI pump, I put in an inline WIX filter/regulator. Then I have 3/8 braided stainless - teflon lined fuel line up to the fuel rail.

The fuel pump I have is supposed to be quiet, but makes all kinds of noise, more than just buzzing. There is an intermittent grinding noise as well. It is loud enough for people to hear it over the engine idling. They constantly ask what is wrong. One of the runs I took last weekend, the pump quit on me completely. And then when it started again it was intermittent, I barely made it back to camp. I just finished tesing the wiring / relay / etc and have come to the conclusion that I bought a bad pump. The company wants me to send it in for testing and replacement. So I believe they think it is bad as well (based on my description).

The question is (a) could a weak/bad fuel pump have cased my P0507 code, and (b) could this have also caused the blinking SES light?

DuoDS

I have just remembered that I may have bought an incorrect MAF sensor. My buggy build took 13 months, and at the beginning I knew I had a 1998 LS1, but later it turned out I ended up running the EFI with a 2002 Z06 ECM. I bought the MAF for the 1998 Camaro Z28 back when I was assembling the engine, but now I find that the 2002 Z06 ECM "requires" a different MAF.

Could this be part of the issue concerning my P0507 code? or could this have contributed to the flashing SES light?

Or will the Z06 ECM operate just fine with the MAF off a 1998 Z28?

So far I am leaning toward two possible causes for these two issues (blinking SES and P0507 code). A possibly broken/weak fuel pump, and using an incorrect MAF.

Still just looking for advice.

96 Comp T/A

iTrader: (8)

I believe if you just disconnect it, it will run in speed density mode. You will get an SES light but it should run.

DuoDS

I'm lookinf to run the sand rail with no SES lights, so if something goes wrong, I can see it and respond immediately. At this point, I am working on trying to get rid of all SES notifications. The blinking SES makes me nervous, the P0507 code doesn't really make sense to me because my engine idles aroud 500-600 rpm all the time.

I would like to solve all these issues so a true SES notification can get my attention in case there really is a problem.

In a sand rail, if I really didn't care, I would not have installed the SES light in the first place.

96 Comp T/A

iTrader: (8)

What I posted was a troubleshooting step, not a final solution. If you disconnect the MAF and that particular code goes away, it might answer your question in regards to the MAF causing the misfire. BTW what transaxle do you run. It seems that market segment is due for a reasonably priced LS compatible transaxle setup.

DuoDS

Thanks for the trouble-shooting step, I will try it and see what happens.

As for your other question, I am not running a traditional dune buggy transaxle mid or rear engine setup. I have my engine front mounted into a race-built TH-400 automatic transmission then a custom drive-line into a Jaguar XJ12 IRS rear end with inboard brakes. Just like the powertrain of a car.

With 12 inches of travel in the front and 10 in the back, this is the smoothest buggy I have ever ridden in (35 years duning).

I should find some pics to post, but you can see the style by looking at SandRocket.com.

Once I get the bugs worked out, it should be awesome. And I am into the entire project around $8K total for the finished buggy including tires, seats, and off-road lights. So I pretty much spent less on the entire sandrail than it costs for one Mendeola transaxle built to handle LS1 power levels.

Pretty good deal I think, plus with the automatic tranny, it is point and shoot!

HPInStyle

I doubt the MAF is your problem unless it's defective. If you can get access to a scan tool, that would probably save you countless time over trying to guess at it.