Please help: Car sounds like a WRX + Rumbles

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Spetz

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Hi guys, I have recently done quite a bit of maintenance on the car and now it sounds like a WRX and has a heavy rumble. Maintenance carried out:
  • Replaced distributor o-ring (was leaking)
  • New distributor cap + rotor
  • New spark plug leads
  • Ultrasonically cleaned injectors
  • Replaced valve stem seals
  • Lifters cleaned out
Symptoms:
  • When I put my hand on the exhaust it fluctuates between pressure and vacuum (so my hand gets sucked onto the tail pipe, then pushed out etc)
  • Though I have not driven it, the rpm hesitate to rise when throttle is given, so lack of power
  • Sounds like a WRX
  • Rumbles/vibrates quite a bit
What I have tried/tested:
  • Checked spark leads are in correct spot - They appear to be correct
  • Disconnected each spark lead out - idles worse on each lead taken out
  • I have disconnected 3 of the front injectors, the middle one seemed to make no difference in idle. Replaced this injector with my old one but made no difference in how it runs
Any help or advice is greatly appreciated
 
Originally Posted By: Spetz
Hi guys, I have recently done quite a bit of maintenance on the car and now it sounds like a WRX and has a heavy rumble. Maintenance carried out:
  • Replaced distributor o-ring (was leaking)
  • New distributor cap + rotor
  • New spark plug leads
  • Ultrasonically cleaned injectors
  • Replaced valve stem seals
  • Lifters cleaned out
Symptoms:
  • When I put my hand on the exhaust it fluctuates between pressure and vacuum (so my hand gets sucked onto the tail pipe, then pushed out etc)
  • Though I have not driven it, the rpm hesitate to rise when throttle is given, so lack of power
  • Sounds like a WRX
  • Rumbles/vibrates quite a bit
What I have tried/tested:
  • Checked spark leads are in correct spot - They appear to be correct
  • Disconnected each spark lead out - idles worse on each lead taken out
  • I have disconnected 3 of the front injectors, the middle one seemed to make no difference in idle. Replaced this injector with my old one but made no difference in how it runs
Any help or advice is greatly appreciated
You don't mention what make or model and engine of the car you're working on so my response will be general. Sounds like you have a dead cylinder. You might want to perform the injector disconnect test on the remaining cylinders to make sure it's just that one front/middle cylinder that's acting up. Anyway, start with the simple stuff. I would first focus in the middle front cylinder, the ignition in particular. Check the resistance of the new spark plug wire. Compare it to the service specs (if available) or re-install the old wire and see what happens. Or, move that new middle wire to another cylinder and repeat unplugging the injector test. If the problem follows the wire, you've found your problem. It's a long shot but I've been fooled before. If it's not the wire, then pull and examine the spark plug. Replace the plug with a new one and see if the problem goes away. Or swap it with one from another cylinder and repeat unplugging the injector test. We'll assume that you've eliminated fuel as a possible cause because you swapped in your old injector. The steps above should eliminate the ignition as a cause. If you still cannot ID the cause after this, I would start looking at mechanical things; compression, etc.
 
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How can I edit the first post? Car is a 3.5L 6G74 2003 Mitsubishi Diamante. I have replaced the injector that seemed to make no difference when disconnected and the issue continued. Also, when seeing as disconnecting each spark lead causes the idle to be worse, would this not mean that all cylinders are firing? I am primarily concerned that I destroyed a valve while doing the stem seals, so it seems unlikely
 
It sounds exactly like a valve issue. Especially if you were in there. Even a nearly dead cylinder may fire, so pulling a plug lead may not diagnose this. Get a compression tester on that thing and get back to us...
 
From research (and I hope I am wrong) but I fear it is a bent valve. Are valves that easy to bend? I just changed the valve stem seals.
 
I believe this uses a timing belt? Is it on 100% correct? When you first put it back together was the belt off a few teeth? Did you crank it with the starter and hear a noise? It is an interference engine so it would be reasonable to suspect a bent valve. Edit: Yes they are easy to bend when hit by the piston.
 
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The timing belt was not taken off. The valve seals were done with everything in place. Rope down the spark plug tube to keep the valves up
 
What kind of valve train does this use mechanical adjuster or hydraulic? Is the lash correct or in the case of a hydraulic are they seated properly. The valves might be too tight for some reason, that would do it.
 
Anyone check the timing? Find out where TDC is on the crank pullly line up with the crankcase mark, and see if the rotor is pointing to the right cylinder.
 
Spetz: Did you do all the work? If you are capable of doing this work I don't understand why you would ask BASIC service questions at this point. I am befuddled. But here's a few Q's: How did you R&R the valve stem seals? Air line method or coiled rope method? Hopefully you've not a bent valvestem. Lets investigate further. You could have pumped up or collapsed a lifter. I hope You didn't disassemble then to clean them - did you just plunge them whilst in a can of kero?
 
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Surely this is SOHC engine with rocker arms. Rockers are removed to gain access to the valves, then no need to remove cams and belt. Hopefully he removed rockers to mechanically disconnect the valves from the cam prior to bringing the rope in contact with the valves.
 
Yes I did everything myself (from reading guides and watching videos) Rope was used to keep the valves up. Rocker arms were of course removed before compressing the rope The distributor was removed yes, but there is only one way it can go back in. Lifters are hydraulic, plunged them in diesel and all were working fine. I assume since the exhaust is sucking in that this means rather than a valve not opening completely, it is in fact an exhaust valve not closing completely?
 
You say it can only go in on way so i assume it has a slotted drive end could it be put in 180 degrees off or are the slots a different size on the left and right sides of the shaft? I need to look at this engine in alldata later instead of using my imagination.
 
It's strange that you could bend a valve so easily, unless the valve timing was way off and you have an interference engine. It sounds like something wasn't done right when you reinstalled the rocker arms. You probably didn't set the TDC correctly when you reinstalled the rocker arms and your valve timing is quite off. I would take them off and set the TDC properly and then reinstall them correctly. So, fix your valve timing. Obtain the OEM repair manual for your car for the correct installation procedure like this ebay CD-ROM. Alternatively consult the repair guides on AutoZone. You many need to create a free account: http://www.autozone.com/autozone/repairi...996b43f8037e895 Your problem is more than likely incorrect valve timing, incorrect valve adjustment, or both. Simply follow the repair guides and do the correct installation and adjustment.
 
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