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Discussion Starter · #1 ·
Hello all,
Seems it never ends on the builds eh? If not the list of improvements, then the little gremlins that pop up…
I had the car out of the garage yesterday just for some cleaning and to get some pics. When I ran into two issues. One is the oil pressure when revving up. This is a new issue and I know it wasn’t there last week when I last had it out for a ride. Idle pressure is great 50-60psi. Revving it up it dips pretty low, like under 15psi. I took it for a light ride and kept an eye on the gauge. Idle, part throttle, even full throttle, it stays strong. It seems to be rpm dependent and nothing to do with load, which I think is a good thing (lesser of two evils). Last fall I had switched from a front sump pan to a rear sump. Obviously I changed the pickup at that time too. From what I’ve read online it seems some folks have had an issue with the pickup sitting so close to the bottom of the pan it hinders oil pickup volume at higher rpm but that seems odd to me as I haven’t noticed it before. I checked oil level and according to the dipstick it’s “full”. This pan is a Ford Racing unit and came with the dipstick so I would HOPE it’s matched to that pan to read accurately. Other thought was maybe the pickup has come loose to some extent and amount of oil it can pull is sufficient at lower rpm and not at higher rpm? Either way the engine sounds healthy and oil looks clean. I’m not getting on it just in case. Even when I did step on it a bit during the test I backed out when I saw it begin to dip. Don’t want to drop to zero pressure especially at 4000 rpm or more!

second issue (and I referenced this in my last thread about it running rich last week during its first major ride) is the sniper o2 is reading full lean. I deactivated the feedback from the o2 which runs it on the last known good file. Running decent that way but still a bit rich (based on my observations, obviously the screen is saying full lean). This is the second o2 I’ve had in this sniper as the same thing happened to the first one. The car has 120 miles on it and less than an hour of run time prior to seeing any miles. I know the o2 is susceptible to thermal shock depending where it’s located but I have it in what I thought was the best compromise I could come up with. Just after the collector on the inside of the pipe and as high up as I could get it (ended up still being about horizontal). Other guys I’ve read about have it in a similar spot and have logged thousands of miles without issue. Only other option I could see is putting it in a single primary to get a more ideal angle and still be out of sight but I’m not a fan of taking a reading off a single cylinder. Again, others who’ve gone that route have had zero issue there as well.

I decided over the winter I was going to sell the car this summer since the market is so strong right now (and who knows, that bubble could burst tomorrow) but I can’t sell it with issues. Aside from the lower money it would bring I just can’t in good conscience sell it without it being right. When I first built this car I had a QFT 750 on it and it ran pretty well (during the go cart stage, still needed fine tuning) before I decided to go with fuel injection. If I can’t get the tune right because of burning up o2 sensors I’d consider going back to carb, but I hate to redo it yet again. If it helps the engine is a 408” stroker, AFR 185 heads, comp XE282HR, and the aforementioned Holley Sniper. Thanks for any feedback!
 

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Factory Five MKIV Roadster 2003 Mach 1 4.6 DOHC
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Hello Datosi, I had the same issue on a previous cobra I owned it had a 1993 5.0 fuel injected motor. One day the oil pressure gauge would display erratic oil pressure readings when the engine warmed up. While driving the oil pressure would drop below 15 PSI. It would intermittently drop to zero PSI and then up to 15 PSI while sitting at a stop light. The car engine didn't sound different, surge or act strange while oil pressure reading was moving around. Seeing the low pressure was disheartening and scary. I hooked up a mechanical gauge and the oil pressure was fine showing above 20 PSI at idle. When the motor was revved it would increase to the proper PSI readings parallel with RPM increase. The conclusion was the Speedhut two post oil pressure sender was faulty. I ordered another one and after about 2k miles the second sender started to do the same erratic oil pressure sweeps.

My current MK4 oil gauge will occasionally fluctuate showing 10 PSI or 5 PSI at a stop light with the motor hot after a drive. Then at the next stop light no fluctuation. My current car also has the Speedhut two post oil pressure sender. It seems to be a common occurrence with these Speedhut oil pressure sending units. Unfortunately I'm not familiar with the SNIPER issues to help. Hopefully someone on here can assist you promptly. Good Luck.
 

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Discussion Starter · #3 ·
I’m embarrassed to say I didn’t even consider that seeing as the idle pressure looked good! As luck would have it, I also have the speedhut two post sending unit! I try a mechanical gauge first before digging any deeper
 

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my 2 post speed hut sender went out suddenly one day. I glanced down and noticed that my pressure was 0. In a panic, I glanced behind me to make sure I didn't have 8qt of oil dripping down the road.
Speedhut should send a free replacement...at least they did for me.
I plugged my sender back into the block, but others will argue to get an extension or use a length of flex line and make a remote location on the frame for the sender. Heat and vibration are though to be the main reasons for the sender unit failure. I have all the things to make a remote location if this next sender fails on me.
And yes, check with a mechanical gauge first to make sure it's the sender issue.
I think speedhut has upgraded their oil pressure sender to a 3 wire one, but requires getting behind the dash and replacing the gauge as well.
 
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Either 10 W 30 or 10 W 40 mobile one synthetic. I can’t remember which
I started with 10w40 and noticed a big drop when I went to 5w30. I went back up on weight.
On the days i was concerned with oil flow I pulled a valve cover and watch the oil circulate.
 

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A vacuum leak on the same side as your O2 sensor will cause a “false” lean reading. I would suggest you pull the spark plugs and compare them.

HTH
Norm
 
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Discussion Starter · #13 ·
A vacuum leak on the same side as your O2 sensor will cause a “false” lean reading. I would suggest you pull the spark plugs and compare them.

HTH
Norm
Thank you. I have pulled the plugs and compared and they’re pretty consistent. There’s a well known issue with the Sniper where when the o2 gets thermally shocked (usually be condensation in the pipe on startup) it’s fried and well read full lean. It would appear that’s where I’m at especially with my less than ideal o2 placement. I have a new o2 on the way with a bung extender to see if that solves the problem. If not I have another idea that might work…
 

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Discussion Starter · #14 ·
So an update on these issues. I reached out to Speedhut and they were more than understanding and have sent out a new oil pressure sending unit at no charge! I think that’s pretty standup of them seeing as I bought the gauges over 6 years ago! Granted, they have very little use, but still, I don’t think they were under any obligation to me to fix the problem.

I’ve also picked up 2 new Bosch o2 sensors for the sniper as well as a bing extender to pull the sensor out of the direct path of whatever liquid might go flying by at startup. I found a seller of the o2 sensors that is roughly half the cost I found them elsewhere and they are the legit real deal Bosch sensor. If I still run into an issue with the new sensor and extender, I’ll likely put a bung in one of the primaries and see how that goes. Wish me luck! I’ll keep y’all posted
 
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