86 Turbo Running Rough when hot/injector questions

[Glassmuseum]

Hi. I have been using Carpokes as an awesome resource since purchasing a 86 944 Turbo. I really appreciate the community and this is my first post.

I have been going through the car and taking care of things as needed. I’m currently stuck on a rough running issue when the car is warm. The tricky thing is I’m not even sure if this was a pre-existing issue because the car is so new to me.

issue: the car usually starts just fine and idles around normal RPM until it gets up to temp and then it starts sputtering like it’s only firing on three cylinders. I did pull off one of the injectors and it ran the same so it seems like it could be something fuel related. I did replace the main fuel lines with Rennbay’s kit, fuel pressure regulator and replaced some vacuum lines.

One thing I will note is that the previous owner replaced the fuel injectors with green tops. I do see that they have the part number 028 150 803 stamped on them. However I checked the impedance and they are 14.4 ohms and I know that Bosch injectors should be 4.5 ohms. Another odd thing is the connectors are super loose and don’t fit well. It seems like you can get some pretty cheap Knock offs on eBay and Amazon and wondering if that’s what I have here. When the car is running rough, I can jiggle the connector a bit and the rpm’s seems to go up but not enough to correct it. So something seems weird.. This made me think that the connectors were bad at first, but since checking the injectors impedance I am wondering if this is the issue.

Any ideas on how to proceed here? I was almost at the point of changing the ev1 connectors but going to hold off to see if there are any other tests I can run here or if these higher impedance injectors are a no go. I found some info on lower impedance injectors being bad for a 951 but not higher ones.Any help is appreciated!

[gb951]

You may have counterfeit injectors. Find some good used original injectors. New ones are NLA.

[Tom]

Hi. I have been using Carpokes as an awesome resource since purchasing a 86 944 Turbo. I really appreciate the community and this is my first post.

I have been going through the car and taking care of things as needed. I’m currently stuck on a rough running issue when the car is warm. The tricky thing is I’m not even sure if this was a pre-existing issue because the car is so new to me.

issue: the car usually starts just fine and idles around normal RPM until it gets up to temp and then it starts sputtering like it’s only firing on three cylinders. I did pull off one of the injectors and it ran the same so it seems like it could be something fuel related. I did replace the main fuel lines with Rennbay’s kit, fuel pressure regulator and replaced some vacuum lines.

One thing I will note is that the previous owner replaced the fuel injectors with green tops. I do see that they have the part number 028 150 803 stamped on them. However I checked the impedance and they are 14.4 ohms and I know that Bosch injectors should be 4.5 ohms. Another odd thing is the connectors are super loose and don’t fit well. It seems like you can get some pretty cheap Knock offs on eBay and Amazon and wondering if that’s what I have here. When the car is running rough, I can jiggle the connector a bit and the rpm’s seems to go up but not enough to correct it. So something seems weird.. This made me think that the connectors were bad at first, but since checking the injectors impedance I am wondering if this is the issue.

Any ideas on how to proceed here? I was almost at the point of changing the ev1 connectors but going to hold off to see if there are any other tests I can run here or if these higher impedance injectors are a no go. I found some info on lower impedance injectors being bad for a 951 but not higher ones.Any help is appreciated!

Welcome aboard -- great to have you. As George said, based on the resistance readings, assuming they are accurate, you may very well have cheap knock off injectors. Check out this set on eBay right now -- green top, stamped with same part number and basically 'look' like 944 turbo injectors, but at $16 a piece brand new, I'd bet the farm they are fake. The connectors may be ill-formed too, explaining the loose connectors. Maybe post some close up pics of your injectors (and weigh them if you have a postage scale or something to weigh them on -- a lot of knock-offs are lighter than the real ones.) Honestly, I'd hold off on doing anything until you get to the bottom of the injectors. My hunch is these injectors are the root of your rough engine and loose connectors.

And... the DME can handle higher impedance injectors (more resistance, less current), but if those are knock offs, there's no telling what the real flow rate is. My guess is they flow less than stock, probably with an ugly/dripping spray pattern. The cold start enrichment masks the lower flow rate until things warm up. While sorting, you can test that theory by setting the FQS to 1 for 3% more fuel, or to 3 for 6% more fuel. Of course, if the connectors are able to clip on securely, that's a whole other problem...

Post some pictures (and weights if you can). I bet we can spot if they are fakes...

fake-injector.jpg (68.85 KiB) Viewed 430 times

[Glassmuseum]

Hi. I have been using Carpokes as an awesome resource since purchasing a 86 944 Turbo. I really appreciate the community and this is my first post.

I have been going through the car and taking care of things as needed. I’m currently stuck on a rough running issue when the car is warm. The tricky thing is I’m not even sure if this was a pre-existing issue because the car is so new to me.

issue: the car usually starts just fine and idles around normal RPM until it gets up to temp and then it starts sputtering like it’s only firing on three cylinders. I did pull off one of the injectors and it ran the same so it seems like it could be something fuel related. I did replace the main fuel lines with Rennbay’s kit, fuel pressure regulator and replaced some vacuum lines.

One thing I will note is that the previous owner replaced the fuel injectors with green tops. I do see that they have the part number 028 150 803 stamped on them. However I checked the impedance and they are 14.4 ohms and I know that Bosch injectors should be 4.5 ohms. Another odd thing is the connectors are super loose and don’t fit well. It seems like you can get some pretty cheap Knock offs on eBay and Amazon and wondering if that’s what I have here. When the car is running rough, I can jiggle the connector a bit and the rpm’s seems to go up but not enough to correct it. So something seems weird.. This made me think that the connectors were bad at first, but since checking the injectors impedance I am wondering if this is the issue.

Any ideas on how to proceed here? I was almost at the point of changing the ev1 connectors but going to hold off to see if there are any other tests I can run here or if these higher impedance injectors are a no go. I found some info on lower impedance injectors being bad for a 951 but not higher ones.Any help is appreciated!

Welcome aboard -- great to have you. As George said, based on the resistance readings, assuming they are accurate, you may very well have cheap knock off injectors. Check out this set on eBay right now -- green top, stamped with same part number and basically 'look' like 944 turbo injectors, but at $16 a piece brand new, I'd bet the farm they are fake. The connectors may be ill-formed too, explaining the loose connectors. Maybe post some close up pics of your injectors (and weigh them if you have a postage scale or something to weigh them on -- a lot of knock-offs are lighter than the real ones.) Honestly, I'd hold off on doing anything until you get to the bottom of the injectors. My hunch is these injectors are the root of your rough engine and loose connectors.

And... the DME can handle higher impedance injectors (more resistance, less current), but if those are knock offs, there's no telling what the real flow rate is. My guess is they flow less than stock, probably with an ugly/dripping spray pattern. The cold start enrichment masks the lower flow rate until things warm up. While sorting, you can test that theory by setting the FQS to 1 for 3% more fuel, or to 3 for 6% more fuel. Of course, if the connectors are able to clip on securely, that's a whole other problem...

Post some pictures (and weights if you can). I bet we can spot if they are fakes...


fake-injector.jpg

Thank you so much! Excited to be here.

I appreciate the response. Yep I would be willing to bet those are likely the same cheapo injectors. I took a couple of pics and also a video showing how flimsy the OEM connectors fit. I had a spare NA injector laying around and those connectors fit just fine and snug. The injectors are still in the car so I can’t weight them but I will try to pull them soon.

If anyone has a spare set of turbo injectors let me know! Looks like that is the road I’m heading down.

[Tom]

Hard to be 100% sure, but I'm thinking those are cheap fakes. Not very scientific but the bright green looks cheap and plasticy compared to the real ones -- much lighter/brighter green too. Also note the lack of Bosch logo and batch numbers in the little stampings pointed out in the original below. And the connectors don't fit right. All of that 'could' be just changes made by Bosch over the years (everyone seems to be making parts cheaper these days), but the kicker is the 14.4 ohm resistance reading. If you double checked that and they all read that high, I'd say there's clear and convincing evidence they are fake.

real-injector.jpg (489 KiB) Viewed 408 times

[Glassmuseum]

Thank you. Yes unfortunately I have a feeling you’re right.

I just wish these were more available. So again, if anyone has a set for sale, lmk!

[Tom]

Thank you. Yes unfortunately I have a feeling you’re right.

I just wish these were more available. So again, if anyone has a set for sale, lmk!

Pelican Parts sells real Bosch injectors for about $100 each. You can also get a used set on eBay and have them cleaned. Or get a set of quality aftermarket injectors (maybe with more flow than stock to give you a little headroom) and scale the chips to match. We're big on DIY Chips here.

[Glassmuseum]

Thank you. Yes unfortunately I have a feeling you’re right.

I just wish these were more available. So again, if anyone has a set for sale, lmk!

Pelican Parts sells real Bosch injectors for about $100 each. You can also get a used set on eBay and have them cleaned. Or get a set of quality aftermarket injectors (maybe with more flow than stock to give you a little headroom) and scale the chips to match. We're big on DIY Chips here.

Unfortunately when you add those pelican Bosch injectors to the cart, they say out of stock. I think they have been NLA for a while. not much on eBay either.

I am very interested to Install a chip in the car but I am thinking I will start from stock first so I can make sure the car is ready and sorted first and then I’ll move to that route.

Now the search starts for some OEM injectors. thanks for all the help here!

[walfreyydo]

Injectors aside, you may want to check the DME temp sensor. This is what tells the DME to switch between cold operation and warm, and affects the air fuel ratio. When the DME temp sensor fails, folks usually get a rough running condition either at cold startup or at warmup, which seems to match your description. This is especially low hanging fruit due to the ease of access and generally low cost of this sensor.

Injectors may still be an issue that must get resolved, but we shouldn't jump to conclusions that this is the cause of the problem. I recommend first starting with the more easy and common cause of this issue which would be the DME temp sensor. If that doesnt solve it, then circle back to the injectors. I believe all the stock injectors on 944s up until about 1990 are low impedance.

[Glassmuseum]

Injectors aside, you may want to check the DME temp sensor. This is what tells the DME to switch between cold operation and warm, and affects the air fuel ratio. When the DME temp sensor fails, folks usually get a rough running condition either at cold startup or at warmup. This is especially low hanging fruit due to the ease of access and generally low cost of this sensor.

Injectors may still be an issue that must get resolved (especially if they are high impedance), but I would say to eliminate the more easy and common things first which would be the DME temp sensor.

Thank you. I actually replaced the dme temp sensor as well for a whole other reason so that is likely ruled out now.

I think something screwy is going on with the injectors. When I wiggle one of the injector connectors while it’s running, it changes the rpm’s. I guess I could change the ev1 connectors ( I have some aftermarket ev1 connectors that do for more snug on these), but I feel like that is just potentially covering up the issue.