The most fun you can have as a parent is TBall followed closely by Little League.

I got my injectors out and ready for the mailman to pick up for WitchHunter tomorrow. The working injectors appeared to be after market and had been replaced once. The bad ones I would assume are original equipment. Only 85,000 miles, but 26 years must be a little too much.

 

the middle two are stock, but look like they've been rebuilt "recently"... let us know what witchhunter says!

 

Ya know... before you send these off to Witchhunter - what does the wiring harness look like at the injectors? (Sorry if you already covered this earlier in the thread, I'm joining a little late...)

 

wait... i just looked closer and it looks like the outer two injectors have different part numbers than the inners. can you take a close look and see if i'm not hallucinating?

 

The wires on the harness don't look bad. The plastic sheathing near cylinder 1 have a few cracks. But the wires themselves are still good.

 

I can barely read the injectors part numbers. They are definitely not the same. The also have a different look. The body (middle part) looks different. However, the overall length from top to bottom is the same and the place where the retaining clip is attached is in the same spot. I just assumed they were different brands and figured it didn't make any difference as long as the flow rate was the same. Should I be concerned about this?

 

if the flow rate is the same, then you're probably fine. maybe include a note w/the shipment to WH mentioning this.

it makes me so sad that so many of these cars were maintained by monkeys over the years.

 

I have to be careful trashing the PO's. This car was given to me by my father in law. He got it from a former business partner and family friend who bought it from the original owner, a Porsche enthusiast. Most of the neglect was probably suffering at the hands of people I know. At this point, I think the independent mechanics I have seen leave a lot to be desired as well. The only way to maintain one is to get your fingernails dirty and become a Rennlist member.

 

I exploded the part number on my 1 and 4 injectors. Looks like I have the wrong part. Bosch 0 280 150 158 is for the non-turbo 85 and up. The ones in 2 and 3 are 0 280 150 803 which is the correct one for the Turbo. The flow rates are not the same. Looks like I need to source a couple of proper fuel injectors.

 

that is correct the middles ones are the correct for turbo application the ones at the end are 944na

 

Hey everyone. I scanned all 6 pages of this thread and i still feel confused as to why my car is cutting out aswell. Basically me and my dad picked up a 87 Guards Red 951 for $4350 with 130k for a project track day car. The car blew a head gasket about 4k miles ago and had everything done on the car to get it back to spec (over $5 grand worth of work and i have receipts) but then was sitting for like 4 years barely driven. It has extensive records and receipts of the work done and is in nice shape.

Anyways when we took the car for a drive a few times we discovered that the car has good power in 1st and 2nd gear full throttle and boosts correctly but then at higher loads in higher gears (3rd and 4th) WOT conditions every time it will cut out. Ive been doing alot of research and it seems like according to everyone talking on the net and clarks garage it is the DME or KLR computer going into overboost protection mode and cutting fuel (sound right)? I checked all the vacuum lines but they all seem ok but the bypass valve might need replacing(need to do a few more tests). Anyways ive heard soooo many different diagnoses like wastegate problems, faulty computers, fuel pressure reg, vacuum lines, tps, afm. We were thinking since we want to track the car we could do a replacement AFM kit for more power and solve the problem. Im not a Porsche expert by any means and im just trying to learn more about turbo systems. What else should I test and how? Anyways any help would be greatly appreciated! Thanks!

 

944Turbo413 - I have been battling this problem for a long time and done a lot of research also. I have been limited as I don't have the ability to data log from the computer. However, to break down the basics of what I have learned....

Overboost is triggered by measurements from the AFM and the RPM's over a period of time.

Only the DME is involved in triggering overboost mode. The KLR has nothing to do with it.

If you think the problem is electrical, there are limited places to look. AFM, DME Computer or Speed and Reference Sensors. The easiest way to determine what the problem is would be to swap for a known good AFM and/or DME computer. I also swapped out the Speed and Reference sensors at one point to see if they made any difference, but I am guessing those are less likely to be the problem. I would guess the issue if electrical is with the AFM.

When I swapped out my AFM for a known good one, my overboost issue was solved, but now I have an extreme running rich issue. I believe my bad AFM masked the running rich problem. In chasing down my running rich issue, I have learned that basic inspection of the vacuum system isn't enough. After I pressurized the system, I found multiple vacuum leaks. For a couple of dollars on a PCV pipe and valve, it is worth the time to manufacture a device to pressurize the system and listen for leaks using soapy water to pinpoint them.

Check your hoses to/from the wastegate and cycling valve as well as the cycling valve itself as a likely mechanical break point. The overboost protection is there in part to keep from blowing a head gasket. I haven't found everything in the clarks garage write up to be completely accurate, but it is a good source.

Check out the 951 FAQ and look closely at the turbo problems section. http://clarks-garage.com

Good hunting! I just got another fuel injector today and I am hoping to fire up the car this evening. Fingers are crossed.

 

I just got in 4 matched 951 injectors for the first time since owning this car. I finally have a running car.

In conclusion, my problem was a bad AFM as someone had adjusted the spring tension on the barn door to mask a rich problem. Once I swapped out the AFM, I had to fix my running rich problem. In the process I have cleaned up a lot of little issues, but the biggest issue was mismatched injectors as 2 were for a 944 NA and 2 were the proper 951 injectors.

I still have a few things left. My idle is a bit too high and I have a leaky rear seal on the cam tower, but at least I know it is back to running. I can save those for the next couple of weekends. Thanks to everyone for their help and thanks to Lart for his great customer service and getting me the parts I needed.

 

My pleasure

 

Hello again! I am currently STILL battling this frustrating overboost problem and resorted to taking it to a well know Porsche Performance shop in CT. Basically on my own I replaced a bunch of the vacuum lines (not all of them) and the bypass valve because the car was blowing off the vac lines because the bypass valve was not working correctly. Anyways I also took off the AFM and managed to pop off the top off it to expose the internals of it. I couldnt find instructions on how to test the AFM so I basically just cleaned all of the contacts thoroughly and put it back on. Absolutely nothing changed.

We took it to the shop and they were able to reproduce the problem finally after having the car for a week and determined that it at least needed a TPS sensor. But then after they replaced it, the car was still getting fuel cut/overboost condition. So THEN they thought that it could be the DME so they took a DME from a known good car and switched it out and it seemed ok. But they had a problem reproducing the problem before because maybe they didnt go full WOT or something so I was doubtfull. So we ordered a new DME from eBay and sent it to the shop and they replaced it and told us everything is good to go. So we pick up the car and guess what.....it wasnt!

The car still cuts out ONLY when you are FULL WOT for a pretty long period of time (usually 3rd/4th/5th gear) then limps for about minute or so and as long as you dont apply boost it idles ok. I noticed it feels like there is a switch when you press the gas pedal all the way down. What does this switch do?? It feels like a kickdown switch on a Automatic car. Ive tried a few times to floor it but not give it quite WOT, just before it feels like the switch is being pressed and it doesnt seem to cut out.

Anyways so what my conclusion is from reading alot and researching is that it could very well be the AFM. Now as you know a new STOCK bosch AFM is like $800 rebuilt. For a little bit more you can get a Lindsey Racing MAF kit which is a huge improvement over stock. I dont wanna just be throwing lots of money into this car and have it not even fix the problem. Any ideas on how I can narrow it down to the AFM??? I read a post from "Van" who said that even if the AFM/TPS voltage measures up good, it still can deviate from the original specs enough to have a mis-match in the info sent to the computer. Any help from anyone would be SOOOO helpful! I just wanna go racing!!! AHHHHHH