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Hey guys I have a 97 Civic with a stock D16Y8. Symptoms: bucking and hesitating acceleration most noticeable it 1st, 2nd, and 3rd gear; between 2-3500 RPM. It doesn’t always do it, but it’s most noticeable with the engine cold. Seems to be running a little rich as well, new plugs are coated black. NO CEL!
What I have done:
-Cleaned throttle body
-Replaced PCV, plugs, wires, dizzy cap/rotor, air filter, fuel filter, MAP sensor (used known working), ignition coil (from a used good dizzy), upstream o2 sensor (HAD codes p0135, p0155)
-Drove with CAT unbolted to determine if clogged
-Cleaned IACV
-Run Redline SI-1 through fuel
-Checked all grounds.My next steps: swap throttle body with a know working one to determine if TPS is acting up even though I DID check calibration and it seemed fine.
Replace the ICM (ignitor). Replace fuel injectors (maybe leaking or clogged?). Check fuel pressure to determine if FPR and pump is working correctly. Check mechanical timing.I try to rule out timing because it is intermittent, and happens only at lower RPM’s, but who knows.
Some times it pulls hard, sometimes it feels laggy.
Any ideas? Am I on the right track? I thought for sure the o2 sensor would have fixed it since I had those codes.
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You are on the right track, and meanwhile are getting a lot maintenance done :). Did you replace the fuel filter? And you can also check the injectors for dirt/clogging visually. But first i would look at the TPS, did you measure the operational range of the sensor to make sure it goes up smooth and doesn’t jump at some point?
How about intake air Temp (IAT) sensor? if you can swap with a working one to see if it helps id try that. Do you have the stock airbox or CAI? Think about what changed right before this started.. even season wise.. if you have a CAI, was this the first winter with it etc…
Do you have an EGR on that motor? Can you check engine vacuum? the leak could seal a little after warming up, hence the result.. Could be other possibilities, but lets start with that
Fuel filter replaced. Pulled and cleaned injectors as well. Yeah operational range of TPS seems normal, no noticeable jumps or skips; although it could change once the engine warms. No EGR here. Did it with stock air intake, and the short ram I replaced that with.
The IAT you mention I thought was a MAF sensor…. HMMMM. I unplugged it and it drove MUCH worse lol, symptoms seemed more severe. I’ll swap it with another if I can find one. How can I check engine vacuum? I do have vacuum pump, where would I hook it up at? Also, idle is fine no surging etc… So maybe a vacuum leak I’ll take a look.
Thank you for your suggestions.
To check the vacuum, unhook the brake booster vacuum hose from the CHECK VALVE (on or inside the hose between manifold and booster) with engine off, and hook it up to your gauge (don’t want to suck anything in there inadvertently). You should get a steady reading (might bounce +-2 psi B/C of age and worn valve guides. Adding gas will make it drop, and releasing gas should make it pop up high for a second and then get back to normal (15-18 psi i believe). Here are some suggestions for diagnosis:
http://www.gregsengine.com/using-a-vacuum-gauge.html
http://www.mysandman.com.au/forums/showthread.php/5340-Vacuum-Gauge-Engine-Diagnosis-ChartI use a hand vacuum pump, the type you use for bleeding the brakes, and it works like a charm. This is also a much easier method for testing back pressure (clogged catalyst 🙁 ), in which case the vacuum would keep dropping as you keep the throttle open. This would’ve saved you the effort of taking it off 🙁
Oh well.. next time 🙂 … I mean hopefully not…
OK, lets put the brakes on here and do some diagnosing. Replacing parts is not a diagnosis. Replacing tune up parts like plugs and the fuel filter was a GREAT start. The other things, not so much. Anytime you have a performance issue, first thing, check for CEL codes. If you don’t have any, move on to the tune up stuff as you have. If there’s still an issue check for vacuum leaks and other possible mechanical causes. So many people forget about mechanical. I type this a lot here. That said, there is more information, even information specific to your vehicle, in this article. For now, table the TPS and other theories that involve sensors that you don’t have evidence of failure for.
http://www.ericthecarguy.com/faq/solving-automotive-performance-issues
Good luck and keep us posted.
Good to hear from you Eric! No replacing parts is NOT a diagnosis, but the majority I replaced were swapped from another Civic. No CEL (I wish!) The TPS is NOT the issue (swapped TB with a known good one). Could not find any vacuum leaks.
Checked fuel pressure today, 33 PSI. Raises when vacuum hose is pulled from FPR, lowers when it’s reconnected. Could not find any vacuum leaks, and idle is solid.
Will be checking compression today if the weather holds out. I’ll post the results.
If there was a compression problem I would think you would have an issue all the time, not just while accelerating. Normally I find issues with the ignition system when there are problems with acceleration. Mainly because I rarely find issues with fuel delivery on Honda’s. I will say that Hondas really don’t like aftermarket ignition components. Especially aftermarket distributors which are a known problem here on this forum. That said, if you have aftermarket ignition parts they would be suspect in my opinion. More information on that as well as a video on how to test your ignition system here.
http://www.ericthecarguy.com/faq/solving-automotive-performance-issues
Good luck and as always keep us posted.
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